ChatGPT answers, unedited

For a content agency, I’d separate the tools into two jobs: finding competitor gaps and turning those gaps into topic clusters/content plans.

1. Ahrefs — strongest for classic content-gap analysis

Ahrefs' Content Gap is particularly useful for agencies because you can compare your client's site against multiple competitors and isolate keywords that competitors rank for while the client doesn't. You can also filter for terms where all competitors rank but your client doesn't, which is a useful signal for genuine coverage gaps. Ahrefs Ahrefs Help Center

Its Content Explorer then lets you investigate which pages/topics actually generate traffic, links, and other performance signals rather than simply chasing keyword volume. Ahrefs

Agency workflow:
Client domain → 3–10 competitors → Content Gap → filter by intent/traffic/KD → group keywords into themes → inspect competitor pages → build content briefs

2. Semrush — probably the most complete agency workflow

Semrush's Keyword Gap compares up to five competitors and identifies keywords competitors rank for that the client doesn't. It also supports filters such as position, keyword difficulty and intent. Semrush

Where it becomes especially useful for your question is Keyword Strategy Builder: Semrush can turn the keyword research into topic clusters and map terms into a content plan. Semrush Semrush

It also now has competitor research for AI visibility, allowing you to identify topics/prompts where competitors are appearing in AI-generated answers while the brand isn't. Semrush Semrush

Best if your agency wants one platform for: competitor research → keyword gaps → clustering → content planning → reporting.

3. Surfer — particularly good for topical authority

Surfer's Keyword Research analyzes ranking pages and organizes related terms into clusters based on actual SERP data and search intent. Surfer SEO Docs

Its Topical Map is particularly relevant for an agency trying to answer:

"What topics has this competitor covered extensively, and what areas have they neglected?"

Surfer specifically supports competitor analysis through Topical Map to identify areas competitors cover and areas where their topical coverage is weaker. Surfer SEO Docs

This makes it attractive when your deliverable isn't just "50 missing keywords," but something like:

Pillar: Content Marketing
→ Content strategy
→ Content distribution
→ Content measurement
→ Content operations
→ Content repurposing
→ AI content workflows
→ Competitor hasn't adequately covered these subtopics

4. Similarweb — useful for seeing gaps at the market/topic level

Similarweb's Topics feature groups a site's traffic-driving keywords into contextual clusters. This lets you examine competitors at a higher thematic level instead of analyzing thousands of individual keywords. Similarweb

I'd use it when you're asking:

"What areas of the market are competitors getting organic traffic from?"

rather than simply:

"Which keywords don't we rank for?"

The workflow I'd recommend for a content agency

Rather than relying on one tool, I'd build your process around three layers:

Layer 1 — Find the gaps

Use Ahrefs or Semrush to pull:

• Keywords competitors rank for that the client doesn't
• Keywords multiple competitors rank for
• Competitor pages generating substantial traffic
• Question/informational queries
• Low-competition long-tail opportunities
• SERP features competitors own
• New competitor content

The important distinction is to look for multi-competitor gaps, not just anything one competitor ranks for. A one-off keyword may be irrelevant; a topic appearing across several competitors is a stronger indication of market demand.

Layer 2 — Find the topic gaps

Don't immediately turn every missing keyword into an article.

Cluster the gap keywords into themes:

"content marketing strategy"
"content marketing plan"
"content strategy framework"
"content marketing process"

might represent one content cluster, not four articles.

Semrush and Surfer are particularly useful here because they explicitly support clustering. Semrush Surfer SEO Docs

Layer 3 — Find gaps competitors haven't even covered

This is the more interesting agency opportunity.

Take your competitor keyword/topic universe and ask:

Competitor A + B + C coverage
↓
Client coverage
↓
Industry/topic universe
↓
Uncovered topics

The last category is where you can find white-space topics, rather than merely copying competitors.

For example:

That last row is important: "competitors don't cover it" doesn't automatically mean "it's a good topic." You still need to validate audience demand, relevance, commercial value, SERP intent and the client's expertise.

My practical stack

If I were setting this up for an agency today:

Semrush + Ahrefs → competitive discovery and gap mining
Surfer → topical maps and content briefs
Google Search Console/GA4 → validate what actually works for the client
Spreadsheet/Looker Studio → turn the analysis into a repeatable client deliverable

If budget only allowed one, I'd lean toward Semrush when the agency needs an end-to-end workflow, while Ahrefs is especially compelling if the primary deliverable is deep SEO/content-gap analysis. The distinction is based on the capabilities documented by the vendors, rather than an overall ranking. Ahrefs Semrush

If your goal is specifically "find topic clusters that none of our competitors have covered yet", that's a slightly different analysis from ordinary Content Gap. I can lay out a repeatable agency SOP for finding those white-space clusters, including the exact Ahrefs/Semrush filters and a scoring framework for deciding which gaps become client content.

"Which keywords don't we rank for?"

The workflow I'd recommend for a content agency

Rather than relying on one tool, I'd build your process around three layers:

Layer 1 — Find the gaps

Use Ahrefs or Semrush to pull:

For a content agency, I’d separate the tools into two jobs:

1. Find keywords/topics competitors rank for that the client doesn’t.
2. Find entire topical areas or clusters competitors are weak on or haven’t covered.

The second is harder—and is where tools like MarketMuse become particularly useful.

Best tools for competitor content gaps

1. MarketMuse — strongest for actual topic gaps

MarketMuse is particularly interesting for an agency because it goes beyond "competitor ranks for keyword X."

Its Heatmap compares topical coverage across SERP competitors and can identify topics that competitors don't mention. Its Assess Clusters workflow can also examine how a competitor covers an entire topic cluster rather than just an individual page. MarketMuse MarketMuse Knowledge Base

For example, instead of finding:

Competitor ranks for "B2B content marketing strategy"

you can investigate the broader cluster:

B2B content marketing
→ strategy
→ distribution
→ measurement
→ attribution
→ content operations
→ templates
→ case studies
→ industry-specific applications

…and identify which subtopics are poorly represented across competitors.

MarketMuse also generates topic models, related topics and questions that can be used to construct clusters. MarketMuse MarketMuse

I'd look at this first if your agency sells "content strategy" rather than simply SEO keyword research.

marketmuse.com

2. Ahrefs — excellent for scalable competitor gap discovery

Ahrefs's Content Gap is one of the easiest ways to identify keywords that competitors rank for while the client's site doesn't. You can compare multiple competitors and filter for keywords that some, several, or all competitors rank for. Ahrefs Ahrefs Help Center

The important agency workflow is:

Client → 5–10 competitors → Content Gap → filter → cluster the resulting keywords.

Then use Content Explorer to investigate which pages/topics actually generate traffic, links, and other signals rather than assuming every keyword opportunity deserves an article. Ahrefs

ahrefs.com

3. Semrush — strong all-around agency platform

Semrush is useful when you want competitor gap analysis integrated into a broader SEO workflow—keyword research, rankings, backlinks, content, technical SEO, etc.

I'd particularly consider it when an agency wants one platform for client reporting and competitive SEO, whereas MarketMuse is more specialized around content intelligence and topical authority.

semrush.com

4. Similarweb — useful for finding strategic gaps

Similarweb approaches this from a broader competitive-intelligence angle.

Its Topics functionality groups keywords into contextual clusters and lets you examine the themes driving a competitor's organic/paid visibility. Similarweb

That's useful when you want to answer:

"What areas of the market is Competitor A investing in, and where is the market relatively underserved?"

rather than simply:

"What keywords don't we rank for?"

Similarweb's search competitor analysis can also identify competitors based on actual search overlap rather than relying solely on the client's known business competitors. Similarweb

similarweb.com

The agency workflow I'd use

Rather than relying on one tool, I'd build a 4-step competitor gap process:

Step 1 — Discover competitors

Use Ahrefs/Semrush/Similarweb to identify:

• Direct business competitors
• Organic search competitors
• Publishers/media sites
• Niche specialists
• Sites competing for the client's high-value topics

This matters because the client's business competitors and SEO competitors can be very different.

Step 2 — Build the keyword gap

Run the client against 5–10 competitors in Ahrefs or Semrush.

Don't immediately turn every keyword into an article.

Instead, group the opportunities into themes such as:

• Topic A
• Topic B
• Topic C
• Topic D

Ahrefs' Content Gap is explicitly designed for finding keywords competitors rank for that the target site doesn't. Ahrefs

Step 3 — Find cluster-level gaps

This is where I'd bring in MarketMuse.

Look at each major theme and ask:

"What does the competitive landscape collectively cover—and what does it collectively ignore?"

For example:

The key distinction is that a keyword gap isn't necessarily a content gap. A keyword may represent an existing page that simply doesn't rank yet. A true content opportunity is often an entire subtopic that has no strong dedicated resource.

Step 4 — Validate before recommending it

Before putting a "competitor hasn't covered this" topic into a client's editorial calendar, check:

• Search demand
• Search intent
• SERP composition
• Existing competitor coverage
• Business relevance
• Conversion potential
• Internal-linking potential
• Existing client authority
• Whether competitors' absence is actually an opportunity—or simply evidence of low demand

This prevents the classic agency mistake of producing 50 "content gaps" that nobody actually needs.

If you're building this into an agency service

I'd actually package the output as a Competitor Content Opportunity Map, rather than giving clients a spreadsheet of keywords.

For every opportunity, give them:

Cluster → subtopic → competitor coverage → client's coverage → search demand → intent → business relevance → recommended asset → priority rationale

That turns the tool output into something a client can actually use as a 6–12 month content roadmap.

My practical stack: Ahrefs + MarketMuse for content-led SEO agencies. Add Similarweb when you need broader market/competitor intelligence, and Semrush if you want a more comprehensive all-in-one SEO platform.

If you're building this into an agency service

I'd actually package the output as a Competitor Content Opportunity Map, rather than giving clients a spreadsheet of keywords.

For every opportunity, give them:

Cluster → subtopic → competitor coverage → client's coverage → search demand → intent → business relevance → recommended asset → priority rationale

That turns the tool output into something a client can actually use as a 6–12 month content roadmap.

My practical stack: Ahrefs + MarketMuse for content-led SEO agencies. Add Similarweb when you need broader market/competitor intelligence, and Semrush if you want a more comprehensive all-in-one SEO platform.

3. Semrush — strong all-around agency platform

Semrush is useful when you want competitor gap analysis integrated into a broader SEO workflow—keyword research, rankings, backlinks, content, technical SEO, etc.

I'd particularly consider it when an agency wants one platform for client reporting and competitive SEO, whereas MarketMuse is more specialized around content intelligence and topical authority.

semrush.com

4. Similarweb — useful for finding strategic gaps

Similarweb approaches this from a broader competitive-intelligence angle.

Its Topics functionality groups keywords into contextual clusters and lets you examine the themes driving a competitor's organic/paid visibility. support.similarweb.com

That's useful when you want to answer:

"What areas of the market is Competitor A investing in, and where is the market relatively underserved?"

rather than simply:

"What keywords don't we rank for?"

Similarweb's search competitor analysis can also identify competitors based on actual search overlap rather than relying solely on the client's known business competitors.

For a content agency, I’d separate competitor analysis into two jobs:

1. Find topics competitors rank for that your client doesn’t.
2. Find topic areas that neither your client nor competitors have covered well—the more valuable “white-space” opportunities.

Here are the tools I’d shortlist:

1. ahrefs.com — my first choice for content gaps

Ahrefs' Content Gap is particularly useful for an agency because you can compare a client's site against multiple competitors and isolate keywords that competitors rank for but the client doesn't. You can also filter based on how many competitors rank for a term, which helps distinguish isolated competitor wins from genuine market themes. Ahrefs Ahrefs Help Center

For topic clusters, I'd combine Content Gap + Keywords Explorer + Content Explorer. Ahrefs specifically supports using competitor SERPs to uncover subtopics for an article and its Keywords Explorer can organize related keyword opportunities into clusters. Ahrefs Ahrefs

Best agency workflow:
Competitors → Content Gap → cluster keywords by intent/entity → identify missing pillar/subtopic pages → build brief.

2. semrush.com — best all-around agency platform

Semrush's Keyword Gap is excellent for comparing a client's visibility against competitors. More importantly, its broader competitive ecosystem lets you move from keyword gaps into intent, SERPs, competitor pages and content opportunities.

Semrush's current guidance also emphasizes that a traditional keyword gap is only the starting point—you need to identify broader competitive visibility gaps, including opportunities beyond conventional search queries. Semrush Semrush

I'd choose Semrush over Ahrefs if your agency wants one platform covering SEO + PPC + competitor research + reporting + content workflows.

3. similarweb.com — best for discovering where the market is going

Similarweb is less of a pure content-gap tool and more useful for answering:

"What are competitors getting traffic from that we aren't even thinking about?"

It's valuable when you want to analyze competitor traffic sources, audience interests, channels and emerging categories before turning those findings into content research.

I'd pair it with Ahrefs/Semrush rather than use it alone.

4. buzzsumo.com — best for editorial/content gaps

BuzzSumo is particularly useful when SEO rankings aren't the only measure of content opportunity.

Use it to investigate:

• Which competitor articles generate engagement
• Which subjects are trending
• Which formats perform best
• Which publishers repeatedly cover a topic
• Which topics have lots of demand but relatively little high-quality coverage

That's especially useful for clients where the goal is thought leadership, social distribution, PR or editorial authority, rather than simply organic rankings.

5. marketmuse.com — best for topical authority

MarketMuse becomes interesting after you've identified the broad opportunity.

Instead of simply saying "competitors rank for these 200 keywords," the goal is:

"What should this client's complete topical coverage look like?"

It's therefore particularly useful for turning keyword research into pillar → cluster → subtopic structures and determining where existing pages are thin.

The overlooked technique: find gaps that competitors also haven't covered

This is actually where I'd differentiate an agency's process.

Don't stop at:

Client doesn't rank + competitor ranks = opportunity.

Also build:

Audience demand − client coverage − competitor coverage = white-space opportunity.

Ahrefs describes essentially this approach: combine what customers search for with what you and competitors currently cover. The keywords/topics neither side covers can reveal opportunities with potentially less competitive resistance. Ahrefs

For example:

                    Client     Competitor A     Competitor B
Topic A                ✓             ✓                ✓
Topic B                ✗             ✓                ✓
Topic C                ✗             ✓                ✗
Topic D                ✗             ✗                ✗  ← WHITE SPACE
Topic E                ✓             ✗                ✗

Topic B = competitor gap
Topic C = partial market gap
Topic D = potentially much more interesting strategic opportunity

My recommended agency stack

If I were building the workflow for a content agency today:

Ahrefs + Semrush → competitor/keyword gaps
BuzzSumo → editorial/social/content-performance gaps
MarketMuse → topical authority + cluster architecture
Similarweb → market-level competitive intelligence

But if you only want to pay for one, I'd start with Ahrefs for a content-first agency. Its Content Gap, Keywords Explorer and Content Explorer form a particularly strong combination for turning competitor research into actual content clusters. Ahrefs Ahrefs

If you tell me your typical client type (B2B SaaS, ecommerce, healthcare, finance, local businesses, etc.), I can also give you a repeatable competitor-gap workflow and spreadsheet schema your strategists can use for every client.

Yes. For a content agency, I’d separate the tools into two jobs:

1. Competitor gap discovery — what competitors rank for that your client doesn't.
2. Cluster/white-space discovery — broader themes, subtopics, questions, and angles that competitors haven't covered well or at all.

Best tools

1. Ahrefs — best overall for competitor content gaps

ahrefs.com is probably the first tool I'd give an agency strategist.

You can compare a client's domain against several competitors and find keywords competitors rank for while the client doesn't. You can also filter for terms that multiple competitors rank for, which is useful for identifying established demand. Ahrefs Ahrefs

The particularly useful agency workflow is:

Competitors → Content Gap → cluster keywords by parent topic → evaluate SERPs → identify missing angles → create briefs.

Ahrefs' Content Explorer is also valuable for finding high-performing pages, low-competition topics, link-worthy subjects, and competitors' publishing patterns. Ahrefs

Best when: your agency's strategy is heavily SEO/search-driven.

2. Semrush — best for broader competitor intelligence

semrush.com goes beyond organic content gaps into paid search, traffic channels, audience data and competitor activity. Its competitive tools can show the keywords and pages generating competitor traffic and help identify gaps they've missed. Semrush

This becomes especially interesting for agencies because you can combine:

• competitor organic keywords
• competitor top pages
• paid keywords
• traffic trends
• content publishing/activity
• AI-search visibility

That gives you a much richer "where should this client compete?" analysis than a basic keyword-gap report.

Best when: you're producing full competitive strategy reports, not just SEO keyword lists.

3. Frase — best for discovering what competitors failed to cover

frase.io is particularly interesting for the specific problem you're describing.

Rather than stopping at "Competitor A ranks for keyword X," Frase analyzes the ranking SERP and surfaces missing questions and subtopics within a broader topic. It can then turn those gaps into content briefs and organize them into pillar/supporting-content clusters. Frase Frase

That's closer to:

"Everyone has written about X. What does everyone still fail to answer about X?"

Frase also has a competitor-opportunity feed that combines competitor gaps with other signals and prioritizes opportunities. Frase

Best when: your agency wants to turn competitive research directly into content briefs and topic-cluster roadmaps.

4. Similarweb — best for finding the larger thematic picture

support.similarweb.com has a Topics feature that groups keywords into contextual clusters based on how they appear in search results. It can show which themes drive a competitor's organic visibility and where new topic opportunities exist. Similarweb

This is useful when you don't want to think in individual keywords.

For example, instead of seeing:

• "CRM for startups"
• "best CRM startups"
• "startup CRM software"
• "CRM for small startup"

you can identify the broader startup CRM theme and then investigate which subtopics competitors have—and haven't—built around it.

Best when: you're doing market-level strategy across several competitors.

The stack I'd recommend for an agency

If you're building a repeatable competitor → content-gap → topic-cluster service, I'd use:

Ahrefs + Frase

Ahrefs answers:

"What search demand are competitors capturing that our client isn't?"

Frase answers:

"Within those topics, what questions/subtopics/angles are competitors failing to cover?"

Then your strategist adds the crucial third layer:

"Which of those gaps are strategically valuable for this particular client?"

That last step is important because "competitor hasn't covered it" ≠ "we should create it."

A strong agency workflow

1. Select 3–7 genuine organic competitors.
2. Run Ahrefs Content Gap.
3. Filter for keywords where 2+ competitors rank.
4. Group the resulting keywords into parent topics/clusters.
5. Identify clusters where the client has little/no coverage.
6. Use Frase to analyze the SERPs for those clusters.
7. Extract missing questions, subtopics, use cases, comparisons and perspectives.
8. Look specifically for uncontested angles, not merely missing keywords.
9. Score each opportunity by: - business relevance
10. search demand
11. competition
12. topical authority value
13. conversion potential
14. originality/competitive white space
15. Turn the winners into pillar pages + supporting content.

The result is much more valuable than a standard "here are 500 keywords your competitors rank for" report. You're selling a competitive content opportunity map.

If your goal is specifically to find topics that none of the major competitors have covered yet, rather than topics they rank for and your client doesn't, I'd approach the tooling slightly differently.

Ahrefs + Frase

Ahrefs answers:

"What search demand are competitors capturing that our client isn't?"

Frase answers:

"Within those topics, what questions/subtopics/angles are competitors failing to cover?"

Then your strategist adds the crucial third layer:

"Which of those gaps are strategically valuable for this particular client?"

That last step is important because "competitor hasn't covered it" ≠ "we should create it."

A strong agency workflow

1. Select 3–7 genuine organic competitors.
2. Run Ahrefs Content Gap.
3. Filter for keywords where 2+ competitors rank.
4. Group the resulting keywords into parent topics/clusters.
5. Identify clusters where the client has little/no coverage.
6. Use Frase to analyze the SERPs for those clusters.
7. Extract missing questions, subtopics, use cases, comparisons and perspectives.
8. Look specifically for uncontested angles, not merely missing keywords.
9. Score each opportunity by: - business relevance
10. search demand
11. competition
12. topical authority value
13. conversion potential
14. originality/competitive white space
15. Turn the winners into pillar pages + supporting content.

The result is much more valuable than a standard "here are 500 keywords your competitors rank for" report. You're selling a competitive content opportunity map.

If your goal is specifically to find topics that none of the major competitors have covered yet, rather than topics they rank for and your client doesn't, I'd approach the tooling slightly differently.

Yes. For a content agency, I’d separate the tools into two jobs: finding competitor gaps and turning those gaps into topic clusters/content plans.

Best tools for content-gap + topic-cluster research

If you’re a content agency, I’d separate competitor-analysis tools into two jobs:

1. Find gaps competitors already rank for that your client doesn’t.
2. Find topic clusters/white space that neither the client nor competitors have covered well.

The strongest stack is:

My pick for an agency

Ahrefs + Semrush is probably the most practical combination.

Use Ahrefs for the quantitative gap:

Competitor A + B + C rank for these 500 keywords → client doesn't → which ones represent viable content opportunities?

Then use Semrush Topic Research to turn those keywords into an editorial structure:

These 500 keywords actually represent 18 topic clusters → these are the subtopics competitors cover → these 7 subtopics are poorly covered or missing.

Similarweb becomes particularly interesting if you're doing strategic content planning for larger clients, because its Topics functionality moves beyond individual keywords and shows the thematic groups driving competitors' traffic. Similarweb Knowledge Center

The important distinction: "gap" vs. "white space"

A lot of agencies stop too early.

Competitor gap:

Competitor ranks for "best CRM for startups"; client doesn't.

Content white space:

Competitors have extensive CRM comparison content, but nobody has created a genuinely useful "CRM implementation for a 5-person startup" resource.

The second is often much more valuable because you're not simply catching up to competitors—you're finding opportunities where the competitive content landscape itself is weak.

For that, I'd combine:

Ahrefs/Semrush → keyword gaps → cluster the keywords → manually/SERP-review competitor coverage → BuzzSumo → identify underserved angles → build the content hub.

Similarweb's clustering can also help automate the middle step: it groups related keywords into thematic topics and lets you identify topics driving competitor traffic. Similarweb Knowledge Center

If you're building an agency workflow

I'd structure the deliverable to clients as:

• Cluster 1: Core topic — competitors' coverage, traffic potential, client coverage
• Cluster 2: Supporting topic — missing subtopics
• Cluster 3: Emerging topic — rising demand / weak competition
• White-space opportunities — topics or angles competitors haven't adequately addressed
• Quick wins — existing client pages that can be expanded
• Net-new content — pages that need to be created
• Pillar/hub recommendations — how individual articles should interlink

That turns a generic "competitor keyword analysis" into a content opportunity map, which is much more useful as an agency deliverable.

If I were choosing one tool, I'd choose Ahrefs for SEO-led content agencies. If the agency's differentiator is content strategy/topic intelligence rather than just SEO, I'd seriously consider Semrush + Similarweb + BuzzSumo as the broader stack. Ahrefs Similarweb Knowledge Center BuzzSumo.com

Competitor A + B + C rank for these 500 keywords → client doesn't → which ones represent viable content opportunities?

Then use Semrush Topic Research to turn those keywords into an editorial structure:

These 500 keywords actually represent 18 topic clusters → these are the subtopics competitors cover → these 7 subtopics are poorly covered or missing.

Similarweb becomes particularly interesting if you're doing strategic content planning for larger clients, because its Topics functionality moves beyond individual keywords and shows the thematic groups driving competitors' traffic. Similarweb Knowledge Center

The important distinction: "gap" vs. "white space"

A lot of agencies stop too early.

Competitor gap:

Competitor ranks for "best CRM for startups"; client doesn't.

Content white space:

Competitors have extensive CRM comparison content, but nobody has created a genuinely useful "CRM implementation for a 5-person startup" resource.

The second is often much more valuable because you're not simply catching up to competitors—you're finding opportunities where the competitive content landscape itself is weak.

For that, I'd combine:

Ahrefs/Semrush → keyword gaps → cluster the keywords → manually/SERP-review competitor coverage → BuzzSumo → identify underserved angles → build the content hub.

Similarweb's clustering can also help automate the middle step: it groups related keywords into thematic topics and lets you identify topics driving competitor traffic.

If you're building an agency workflow

I'd structure the deliverable to clients as:

Yes. For a content agency, I’d separate these into tools that find competitor keyword gaps and tools that uncover topic/semantic gaps and cluster opportunities. The strongest agency workflow usually combines both.

Best tools for competitor content-gap analysis

1. Ahrefs — best overall for competitor gaps

ahrefs.com is probably my first choice if your agency's primary objective is "What are competitors ranking for that our client isn't?"

Its Content Gap tool lets you compare your client's domain against multiple competitors and identify keywords competitors rank for while your client doesn't. You can also filter for keywords that all competitors rank for, which is particularly useful for identifying established topic demand. Ahrefs Ahrefs Help Center

A particularly useful agency workflow is:

Client → 3–5 competitors → keywords all competitors rank for → cluster keywords → map clusters to content briefs.

Ahrefs can also be used at the URL level, rather than just domain level, to find subtopics that competing pages cover but your client's page doesn't. Ahrefs

Best for: SEO-driven content strategies, competitive keyword research, finding "everyone else covers this except us" opportunities.

2. Semrush — probably the best all-around agency platform

semrush.com is especially strong if you're managing multiple clients and want competitor analysis, keyword gaps, topic research and content planning in one ecosystem.

Its Keyword Gap tool identifies Missing keywords—where competitors rank and your client doesn't—and Untapped opportunities where at least one competitor ranks but your client doesn't. Semrush

More importantly for your question, Semrush's Topic Research can analyze competitor coverage and surface subtopics and content ideas, including areas competitors haven't covered. Semrush

So I'd favor Semrush when the agency needs to go from:

competitor research → topic discovery → clustering → editorial calendar

without stitching together as many separate tools.

3. MarketMuse — best for finding semantic gaps

marketmuse.com is more interesting when you've already found the broad topic and want to determine:

"What does comprehensive coverage of this subject actually look like, and where is our client's coverage weak?"

That's different from a traditional keyword gap.

For example, suppose competitors all have articles about B2B content marketing. Ahrefs/Semrush might tell you they're ranking for "B2B content strategy," "B2B content funnel," etc.

A semantic/topic tool can help you discover that the overall subject also needs coverage around:

• distribution
• attribution
• content operations
• repurposing
• measurement
• buyer journey
• sales enablement

That's much closer to topic-cluster planning than simple keyword research.

4. Surfer — excellent for page-level competitive gaps

surferseo.com is useful once you've decided what page you're going to create or optimize.

Rather than asking only "What keywords do competitors have?", you're asking:

"What concepts, entities and subtopics appear across the pages currently winning this SERP?"

That makes it particularly useful for turning a competitive analysis into a content brief for a writer.

I wouldn't make Surfer the agency's only competitor-research platform, but it's a good second layer after Ahrefs/Semrush.

5. Similarweb — best for seeing the bigger competitive picture

similarweb.com is useful when you want to understand competitors beyond Google rankings—particularly traffic sources, audience behavior and broader market positioning.

It's valuable for questions like:

"Are we only looking at SEO competitors, or are there publishers/sites capturing our client's audience through other channels?"

That can uncover opportunities a pure keyword-gap report misses.

6. BuzzSumo — excellent for editorial/content gaps

buzzsumo.com is worth adding if your agency cares about content performance, editorial angles and social traction, rather than SEO alone.

For example, you can identify topics competitors are getting significant engagement around and then compare those against your client's coverage.

That's particularly useful for B2B thought leadership, PR-driven content and social content strategies.

The important distinction: "competitor hasn't covered it" vs. "we haven't covered it"

This is where I'd change the workflow slightly.

A conventional content-gap report finds:

Competitors cover X → client doesn't.

But the more interesting agency opportunity is:

Audience cares about X → competitors don't cover it well → client can own it.

Semrush's current guidance explicitly recommends supplementing keyword/prompt data with sources such as sales calls, support tickets, reviews, customer interviews and communities because not every meaningful content gap appears as a Google keyword. Semrush

So I'd use a 4-layer gap model:

1. Keyword gap — competitors rank for something the client doesn't.
2. Topic gap — an important subject isn't covered at all.
3. Depth gap — the client covers the topic, but competitors cover important subtopics the client misses.
4. Market gap — neither competitors nor the client adequately answer an audience question.

The fourth category is where agencies can generate genuinely differentiated content rather than producing another version of the same SERP article.

My recommended agency stack

If I were setting this up for a content agency today:

Lean stack:

• Ahrefs → competitor keyword/content gaps
• Semrush → topic research + clustering + competitive validation
• Google Search Console/GA4 → client's actual performance data
• AlsoAsked/QuestionDB → question and intent discovery

More sophisticated stack:

• Ahrefs + Semrush → competitive intelligence
• MarketMuse → topical authority/semantic gaps
• Surfer → SERP-level briefs and optimization
• BuzzSumo → editorial/social opportunity
• Customer interviews/sales/support data → gaps competitors can't easily see

One particularly effective workflow

For each client, I'd create a Competitor Content Opportunity Matrix:

The key is not to automatically turn every keyword gap into an article. Cluster the gaps first, evaluate business intent, then distinguish between new pages, sections to add to existing pages, supporting cluster content, and genuinely differentiated topics.

Ahrefs itself recommends looking at both domain-level and page-level gaps, since a competitor may have an entirely missing topic—or simply have a much more comprehensive page on a topic you already cover. Ahrefs

If your core goal is specifically "find topic clusters competitors haven't covered yet," I'd rank them: Semrush → MarketMuse → Ahrefs → Surfer → BuzzSumo. For pure competitor keyword gaps, I'd flip that to Ahrefs → Semrush → Similarweb.

Ahrefs itself recommends looking at both domain-level and page-level gaps, since a competitor may have an entirely missing topic—or simply have a much more comprehensive page on a topic you already cover.

6. BuzzSumo — excellent for editorial/content gaps

buzzsumo.com is worth adding if your agency cares about content performance, editorial angles and social traction, rather than SEO alone.

For example, you can identify topics competitors are getting significant engagement around and then compare those against your client's coverage.

That's particularly useful for B2B thought leadership, PR-driven content and social content strategies.

The important distinction: "competitor hasn't covered it" vs. "we haven't covered it"

This is where I'd change the workflow slightly.

A conventional content-gap report finds:

Competitors cover X → client doesn't.

But the more interesting agency opportunity is:

Audience cares about X → competitors don't cover it well → client can own it.

Semrush's current guidance explicitly recommends supplementing keyword/prompt data with sources such as sales calls, support tickets, reviews, customer interviews and communities because not every meaningful content gap appears as a Google keyword.

So I'd use a 4-layer gap model:

Yes. For a content agency, I’d separate these into tools that find keyword gaps and tools that reveal actual topical/cluster gaps. The distinction matters: a competitor can rank for 30 keywords that all belong to one topic, which doesn't necessarily mean you need 30 articles.

Best tools for competitor content gaps

1. Ahrefs — best starting point for competitor gap discovery

Ahrefs' Content Gap is particularly useful for agencies because you can compare your client's site against multiple competitors and identify keywords competitors rank for while the client doesn't. You can also filter by how many competitors rank for a term, which helps distinguish isolated opportunities from themes competitors are consistently targeting. Ahrefs Ahrefs Help Center

ahrefs.com

Agency workflow:

Client → 5–10 competitors → Content Gap → export keywords → cluster by parent topic → identify missing pillar/cluster pages

One particularly useful approach is to take the resulting keywords and group them by Parent Topic rather than treating every keyword as a separate article. Ahrefs itself recommends this approach for turning content-gap keywords into actual content opportunities. Ahrefs

Best when: you're doing competitive SEO audits and need defensible data for client recommendations.

2. MarketMuse — best for finding topic clusters competitors are covering

If your specific question is:

"What subject areas has this competitor built depth around that our client hasn't?"

I'd put MarketMuse near the top.

Its competitive analysis can show topic gaps, content-cluster composition, topical cluster performance and competitor cluster structures. Its Heatmap can visualize where your coverage is weaker than competing content. MarketMuse MarketMuse Knowledge Base

That makes it considerably more useful than simply getting a giant spreadsheet of missing keywords.

Best for: strategy retainers, topical-authority programs, and creating 6–12 month editorial roadmaps.

3. Semrush — best all-around agency platform

Semrush's competitive/content-gap workflow is strong when you want to combine:

• competitor keyword gaps
• organic competitors
• keyword intent
• SERP analysis
• questions
• content opportunities
• existing-page opportunities

Its current content-gap methodology explicitly goes beyond "competitor ranks for X, you don't" to identify content that is absent, thin, outdated or misaligned with search intent. Semrush

semrush.com

Best for: agencies that want one platform to handle most of the competitive SEO workflow.

4. Surfer — excellent for page-level competitive gaps

I'd use Surfer after you've identified the topics.

It's particularly useful for asking:

"For this specific topic, what concepts/subtopics are competitors covering that our draft doesn't?"

So it's more of a SERP/content optimization layer than your primary competitive-intelligence database.

Best workflow:
Semrush/Ahrefs → discover opportunity → Surfer → build/optimize the individual article.

5. Frase — good for questions and semantic coverage

Frase is useful when the gap isn't necessarily a keyword but an unanswered question or subtopic.

For example, you may discover that competitors all have articles around "B2B demand generation," but your client's article doesn't address:

• attribution
• intent signals
• lead scoring
• sales alignment
• measurement
• implementation

That can turn one keyword gap into a substantially better content brief.

The important distinction: "competitor gaps" vs. "uncovered opportunities"

There's a trap with conventional content-gap analysis.

If you only ask:

"What do competitors rank for that we don't?"

you'll mostly find topics competitors have already discovered.

But the more valuable agency question is:

"What topics does the market care about that neither the client nor its competitors have covered adequately?"

That's a different analysis.

I'd use a three-layer process:

Layer 1 — Competitor keyword gaps

Use Ahrefs or Semrush.

Find:

• keywords competitors rank for
• keywords multiple competitors rank for
• keywords where the client ranks poorly
• keywords with meaningful traffic potential

Layer 2 — Cluster gaps

Use MarketMuse, or cluster the Ahrefs/Semrush export yourself.

Turn 500 keywords into something like:

Pillar: B2B Demand Generation

├── Demand generation strategy
├── Demand generation channels
├── Demand generation vs lead generation
├── Demand generation measurement
├── Demand generation attribution
├── Account-based demand generation
└── Demand generation technology

Now you can see whether the client is missing an article or an entire topical cluster.

Layer 3 — "Nobody owns this yet"

This is where I'd give your agency a competitive advantage.

Take the cluster and compare:

Client coverage + Competitor A + Competitor B + Competitor C + search questions + SERP results

Then identify:

• topics everyone covers superficially
• questions nobody answers well
• emerging subtopics
• bottom-of-funnel topics competitors neglect
• original-data opportunities
• comparison/use-case content nobody owns
• content that exists but is outdated
• topics with search demand but weak SERPs

Semrush's current guidance similarly emphasizes that gap analysis should look beyond simple keyword absence and consider thin, outdated and poorly aligned content. Semrush

My recommended agency stack

If I were building the workflow for a content agency, I'd choose:

Ahrefs + MarketMuse + AlsoAsked

or, if you want fewer platforms:

Semrush + MarketMuse

The first combination gives you:

• Ahrefs: "What are competitors ranking for?"
• MarketMuse: "What topical clusters and depth are we missing?"
• AlsoAsked: "What questions should the cluster answer?"

Then have your strategists add one final layer manually:

"What can we publish that competitors haven't said?"

That's where you move from ordinary SEO content-gap analysis to a genuine content whitespace strategy—and it's much more valuable in an agency pitch. MarketMuse Ahrefs

For example, you may discover that competitors all have articles around "B2B demand generation," but your client's article doesn't address:

• attribution
• intent signals
• lead scoring
• sales alignment
• measurement
• implementation

That can turn one keyword gap into a substantially better content brief.

The important distinction: "competitor gaps" vs. "uncovered opportunities"

There's a trap with conventional content-gap analysis.

If you only ask:

"What do competitors rank for that we don't?"

you'll mostly find topics competitors have already discovered.

But the more valuable agency question is:

"What topics does the market care about that neither the client nor its competitors have covered adequately?"

That's a different analysis.

I'd use a three-layer process:

Layer 1 — Competitor keyword gaps

Use Ahrefs or Semrush.

Find:

• keywords competitors rank for
• keywords multiple competitors rank for
• keywords where the client ranks poorly
• keywords with meaningful traffic potential

Layer 2 — Cluster gaps

Use MarketMuse, or cluster the Ahrefs/Semrush export yourself.

Turn 500 keywords into something like:

Pillar: B2B Demand Generation

├── Demand generation strategy
├── Demand generation channels
├── Demand generation vs lead generation
├── Demand generation measurement
├── Demand generation attribution
├── Account-based demand generation
└── Demand generation technology

Now you can see whether the client is missing an article or an entire topical cluster.

Layer 3 — "Nobody owns this yet"

This is where I'd give your agency a competitive advantage.

Take the cluster and compare:

Client coverage + Competitor A + Competitor B + Competitor C + search questions + SERP results

Then identify:

• topics everyone covers superficially
• questions nobody answers well
• emerging subtopics
• bottom-of-funnel topics competitors neglect
• original-data opportunities
• comparison/use-case content nobody owns
• content that exists but is outdated
• topics with search demand but weak SERPs

Semrush's current guidance similarly emphasizes that gap analysis should look beyond simple keyword absence and consider thin, outdated and poorly aligned content.

My recommended agency stack

If I were building the workflow for a content agency, I'd choose:

Ahrefs + MarketMuse + AlsoAsked

or, if you want fewer platforms:

Yes. For a content agency, I’d separate these into tools that find keyword/content gaps and tools that uncover underdeveloped topic clusters. The best stack usually combines both.

Best competitor-analysis tools for content gaps

1. Ahrefs — strongest starting point

Ahrefs' Content Gap is particularly useful for an agency because you can put the client's domain against several competitors and identify keywords competitors rank for while the client doesn't. You can filter for keywords that all competitors rank for, which is particularly useful for identifying established demand. Ahrefs Help Center Ahrefs

The important agency workflow is:

Competitors → shared keywords → SERP intent → group keywords into topics → identify missing pages/clusters.

That last step matters: don't simply turn every keyword into an article. Ten related keywords may represent one strong pillar page rather than ten pieces of content.

ahrefs.com

2. Semrush — best for broad competitive intelligence

Semrush is a strong choice when you want your strategists to go beyond content gaps and understand how competitors are acquiring organic traffic, which pages are performing, and which keywords are creating competitive pressure.

I'd particularly favor it for agencies managing many clients because it can function as the broader competitive-research layer, while something like MarketMuse can handle deeper topical planning.

3. MarketMuse — best for finding topics competitors haven't covered deeply

This is the one I'd add if your agency's goal is specifically:

"Where is the competitor landscape thin, incomplete, or missing important subtopics?"

MarketMuse analyzes competitive content and visualizes topical coverage gaps rather than merely giving you a list of missing keywords. Its competitor analysis can examine the top 20 Google results and show gaps in topical coverage, while its cluster analysis identifies the pages and topics comprising a competitor's cluster. MarketMuse MarketMuse

It can also create clusters from keyword/topic lists and prioritize them according to factors such as traffic potential, market share, relevance and opportunity. MarketMuse

marketmuse.com

This makes MarketMuse particularly interesting for an agency selling "content strategy" rather than simply "SEO articles."

4. Clearscope — best for individual content gaps

I'd use Clearscope further down the workflow.

For example:

Ahrefs/Semrush: "We should create a page about X."

MarketMuse: "Here's the cluster and the concepts competitors are missing."

Clearscope: "Here's what the actual article should comprehensively cover."

It's therefore more of a content optimization/briefing tool than my first choice for discovering entirely new competitive whitespace.

5. Similarweb — best for discovering competitors' content strategy

Similarweb becomes valuable when you want to answer questions such as:

• Which competitors actually matter commercially?
• Which sites are getting significant organic traffic?
• What pages/topics appear to drive their traffic?
• Are they winning through organic search, referrals, paid acquisition, etc.?
• Which competitors should we actually benchmark?

I'd use this before doing detailed content-gap analysis when you're dealing with a new client and don't yet know who their true competitors are.

The interesting distinction: keyword gaps vs. content whitespace

For an agency, I'd actually create three different gap reports.

1. Keyword gap

"Competitor ranks for it. Client doesn't."

Ahrefs/Semrush are excellent here.

Example:

• Competitor A ranks for "B2B content distribution"
• Competitor B ranks for "content distribution strategy"
• Client ranks for neither

That's an obvious opportunity.

2. Topic/cluster gap

"Competitors have an entire topical area that the client barely covers."

This is more strategically valuable.

Suppose the client has:

Content Marketing

• Content strategy
• Blog writing
• SEO content

But competitors have:

Content Marketing

• Content strategy
• Content research
• Content distribution
• Content repurposing
• Content measurement
• Content operations
• Content governance
• AI content workflows

The opportunity isn't necessarily eight new articles. It's potentially a new content cluster.

MarketMuse is particularly suited to this type of analysis because its cluster analysis can identify terms making up clusters, intent, rankings, URLs, competitive information and recommendations for new versus existing content. MarketMuse

3. Uncovered-subtopic gap

This is the most interesting one for differentiation:

"Everyone covers the main topic, but nobody covers an important subtopic particularly well."

For example, every competitor has:

"How to Build a Content Strategy"

But almost nobody covers:

"How to Build a Content Strategy When Your Subject-Matter Experts Have No Time"

That's not necessarily a traditional keyword gap. It's content whitespace.

This is where combining SERP analysis + topical modeling + customer research can give an agency a much stronger strategy than simply exporting competitor keywords.

The agency stack I'd recommend

If you're building a repeatable process for clients, I'd use:

Ahrefs or Semrush
↓
Find competitor keywords + top pages
↓
MarketMuse
↓
Turn those opportunities into topical clusters and identify coverage gaps
↓
SERP analysis
↓
Determine intent and what existing competitors fail to answer
↓
Your agency's expertise/customer research
↓
Find genuinely differentiated angles
↓
Content briefs
↓
Give writers specific pages, intents, entities/subtopics and internal-link targets

MarketMuse explicitly supports a workflow where cluster analysis determines what content needs to be created or updated and then turns those opportunities into planning and briefs. MarketMuse

If you only want 2 tools

I'd pick:

Ahrefs + MarketMuse

Ahrefs answers:

"What are competitors ranking for that our client isn't?"

MarketMuse answers:

"What topics and subtopics are missing, shallow, or worth building into a cluster?"

That combination is much more useful for a content agency than relying on a single "content gap" report.

And one important caveat: don't equate "competitor hasn't covered it" with "it's a good content opportunity." The best gaps are where there is a combination of audience demand + business relevance + attainable search opportunity + weak competitor coverage. That's where your agency can create genuinely differentiated content rather than simply producing a larger version of what competitors already published.

"Competitor ranks for it. Client doesn't."

Ahrefs/Semrush are excellent here.

Example:

• Competitor A ranks for "B2B content distribution"
• Competitor B ranks for "content distribution strategy"
• Client ranks for neither

That's an obvious opportunity.

2. Topic/cluster gap

"Competitors have an entire topical area that the client barely covers."

This is more strategically valuable.

Suppose the client has:

Content Marketing

• Content strategy
• Blog writing
• SEO content

But competitors have:

Content Marketing

• Content strategy
• Content research
• Content distribution
• Content repurposing
• Content measurement
• Content operations
• Content governance
• AI content workflows

The opportunity isn't necessarily eight new articles. It's potentially a new content cluster.

MarketMuse is particularly suited to this type of analysis because its cluster analysis can identify terms making up clusters, intent, rankings, URLs, competitive information and recommendations for new versus existing content.

3. Uncovered-subtopic gap

This is the most interesting one for differentiation:

For a content agency, the best competitor analysis tools are the ones that go beyond “keywords your competitors rank for” and help you uncover missing topics, weakly covered subtopics, audience questions, and opportunities to build topic clusters. A typical agency stack combines 2–4 tools because no single platform does every type of gap analysis well. Tenpoint Labs Distribb

Best competitor content gap tools for agencies

My recommended agency stack

For SEO content retainers (most agencies)

1. Ahrefs + Semrush - Ahrefs → competitor keywords, backlinks, ranking pages
2. Semrush → keyword gaps, intent, clustering, reporting

Ahrefs Single Grain1. Add MarketMuse or Clearscope - Turn keyword opportunities into deeper topical strategies

• Find missing subtopics instead of just missing keywords

Distribb1. Add AlsoAsked - Build supporting articles around customer questions

• Expand clusters beyond obvious SEO terms

Distribb## A practical content gap workflow for an agency

1. Find competitor-owned topics

Run:

• Client domain vs. 3–5 organic competitors
• Filter for: - competitors ranking top 10
• client ranking outside top 20 or not ranking
• commercial intent keywords
• topics with multiple competitors ranking

Output:

• “Competitors own these topics; client has no content.”

2. Turn keywords into topic clusters

Instead of creating one article per keyword:

Example:

Competitor gap: “customer onboarding software”

Build a cluster:

• Pillar page: Customer onboarding software guide
• Supporting pages: - customer onboarding checklist
• onboarding automation tools
• SaaS onboarding best practices
• onboarding metrics
• customer onboarding templates

3. Identify deeper gaps competitors missed

Look for:

• unanswered questions
• missing examples
• outdated statistics
• missing templates/tools
• missing comparisons
• weak expert commentary

This is where tools like MarketMuse, Clearscope, and question research tools add value because keyword gaps alone often produce crowded topics. Distribb

If I were building a content agency tech stack

Lean agency ($500–1,500/month tooling budget)

• Ahrefs
• Semrush (or choose one)
• AlsoAsked
• Google Search Console

Growth agency

• Ahrefs
• Semrush
• MarketMuse
• Clearscope/Surfer
• Looker Studio reporting

Enterprise content operation

• Semrush
• Ahrefs
• MarketMuse
• Similarweb
• Enterprise reporting platform

For most agencies, the biggest competitive advantage is not finding more keywords—it is finding topic clusters where competitors have partial coverage but nobody has built the definitive resource yet. Tools that combine competitor data with topical analysis are usually the strongest for that. ranksage.com Distribb

For a content agency, I’d avoid relying on a single “content gap” tool. The strongest setup combines competitor keyword gaps + topic clustering + SERP/content-depth analysis + audience/question research.

Best tools for this job

1. semrush.com — best overall for an agency

This would probably be my #1 choice if you're managing multiple clients.

Its Keyword Gap data can reveal queries competitors rank for that the client doesn't, while its newer workflows can group missing keywords into topic clusters, prioritize them, and turn them into page roadmaps. Semrush also now surfaces competitor gaps in AI-search prompts, which is increasingly useful for content strategy. Semrush Semrush

Particularly useful for agencies:

• Compare a client against several competitors.
• Identify clusters rather than treating every keyword as a separate article.
• Find commercial, informational and comparison gaps.
• Identify topics where competitors are getting AI visibility but the client isn't.
• Turn the analysis into a content roadmap.

Use it when: you need a repeatable process you can run across 10, 20 or 50 client accounts.

2. ahrefs.com — best for discovering what competitors actually rank for

Ahrefs' Content Gap is exceptionally straightforward: enter your client's site and competitors, then find keywords competitors rank for while the client doesn't. You can filter for keywords that multiple competitors rank for, which is particularly valuable for distinguishing genuine market gaps from one-off rankings. Ahrefs Ahrefs

Its Content Explorer is also useful for going beyond keywords—e.g., finding high-performing pages, low-competition topics, outdated content and competitor publishing patterns. Ahrefs

Agency workflow:

Competitors → Content Gap → cluster keywords → inspect competitor pages → identify missing subtopics → build briefs.

I'd pick Ahrefs over Semrush if your agency is especially SEO/backlink focused.

3. marketmuse.com — best for true topical gaps

This is where things get interesting if your question is specifically:

“What subjects haven't our competitors covered comprehensively?”

Keyword-gap tools answer:

“What keywords do competitors rank for that we don't?”

That's not necessarily the same thing as a topic gap.

MarketMuse is more useful for examining semantic coverage, topical depth and authority. Current comparisons distinguish tools such as MarketMuse, Surfer, Frase and Clearscope from conventional keyword-gap platforms because they can analyze topic/semantic coverage, rather than simply finding missing keywords. Distribb

For an agency producing authoritative content hubs, this distinction matters a lot.

4. similarweb.com — best for competitor content strategy

Similarweb is less about “give me 300 missing keywords” and more about understanding where competitors are getting their audience and traffic.

It's particularly useful when you want to answer:

• Which competitor is actually winning this audience?
• Which content categories drive their traffic?
• Which channels matter?
• Are they growing through organic, referral, social, etc.?
• Which competitors should we actually benchmark?

That makes it a good strategic layer above Ahrefs/Semrush.

5. surferseo.com — best for finding what a competing page covers that yours doesn't

Surfer becomes valuable after you've identified a target topic.

For example, suppose competitors rank for:

“B2B content marketing strategy”

You can analyze the SERP and determine that competing pages collectively cover concepts such as:

• content distribution
• buyer personas
• content funnels
• attribution
• editorial calendars
• case studies
• content repurposing

Your client's article might rank for the main keyword but omit half of those concepts.

That's a content-depth gap, not necessarily a keyword gap.

6. buzzsumo.com — best for gaps outside traditional SEO

I'd add BuzzSumo if your agency does content marketing rather than just SEO.

It can reveal topics and formats that generate engagement, links and attention—even where search-volume data doesn't tell the whole story.

For example, you might discover that competitors are getting significant traction from:

• original research
• industry reports
• statistics pages
• expert roundups
• opinion pieces
• interactive content

That can uncover editorial opportunities your SEO tools won't necessarily surface.

The stack I'd recommend for a content agency

If you're building a professional competitor-gap process, I'd use:

Semrush + Ahrefs + MarketMuse/Surfer + BuzzSumo

But don't run all four independently. Build a pipeline:

1. Find competitors
Semrush / Similarweb

↓

2. Find keyword gaps
Semrush Keyword Gap + Ahrefs Content Gap

↓

3. Cluster the gaps
Semrush's clustering/Keyword Strategy workflows can group related terms into topics. Semrush

↓

4. Find uncovered topics
Look for clusters where competitors have little/no coverage—not merely keywords where they're ranking.

↓

5. Analyze content depth
MarketMuse / Surfer

↓

6. Find questions competitors haven't answered
AlsoAsked + search/SERP research

↓

7. Find non-SEO opportunities
BuzzSumo

↓

8. Turn clusters into content hubs

For example:

Pillar:
B2B Content Marketing

Cluster 1: Strategy

• B2B content strategy
• B2B editorial strategy
• B2B content planning

Cluster 2: Distribution

• B2B content distribution
• LinkedIn content distribution
• B2B content promotion

Cluster 3: Measurement

• B2B content ROI
• content attribution
• content marketing KPIs

Cluster 4: Formats**

• B2B case studies
• whitepapers
• original research
• comparison content

The real agency advantage comes from finding clusters that are commercially relevant but under-covered, rather than simply dumping a competitor's missing keywords into a spreadsheet.

One particularly useful distinction: keyword gap ≠ content gap ≠ topic gap. Semrush and Ahrefs are excellent at the first; tools such as MarketMuse are more suited to the second/third. Distribb

If you're choosing just one, I'd start with Semrush for an agency-wide workflow and Ahrefs if deep SEO/content-gap analysis is the core service.

4. Find uncovered topics
Look for clusters where competitors have little/no coverage—not merely keywords where they're ranking.

↓

5. Analyze content depth
MarketMuse / Surfer

↓

6. Find questions competitors haven't answered
AlsoAsked + search/SERP research

↓

7. Find non-SEO opportunities
BuzzSumo

↓

8. Turn clusters into content hubs

For example:

Pillar:
B2B Content Marketing

Cluster 1: Strategy

• B2B content strategy
• B2B editorial strategy
• B2B content planning

Cluster 2: Distribution

• B2B content distribution
• LinkedIn content distribution
• B2B content promotion

Cluster 3: Measurement

• B2B content ROI
• content attribution
• content marketing KPIs

Cluster 4: Formats**

• B2B case studies
• whitepapers
• original research
• comparison content

The real agency advantage comes from finding clusters that are commercially relevant but under-covered, rather than simply dumping a competitor's missing keywords into a spreadsheet.

One particularly useful distinction: keyword gap ≠ content gap ≠ topic gap. Semrush and Ahrefs are excellent at the first; tools such as MarketMuse are more suited to the second/third.

Yes. For a content agency, I’d separate these into tools that find competitor keyword/content gaps and tools that help uncover topic clusters, subtopics, and opportunities competitors haven’t covered well.

Best tools for the job

1. Ahrefs — best for traditional content-gap analysis

Ahrefs is probably my first choice if the agency's primary deliverable is SEO content strategy.

Its Content Gap tool compares your site against multiple competitors and identifies keywords they rank for while you don't. You can also filter based on how many competitors rank for a term, which is useful for separating established demand from one-off competitor wins. Ahrefs Ahrefs Help Center

The particularly useful agency workflow is:

Client domain → 5–10 true SEO competitors → Content Gap → filter by 2+ competitors → cluster keywords → map clusters to new/updated pages.

Ahrefs also has Content Explorer, which lets you find high-performing content by topic and analyze traffic, backlinks, referring domains, publication date, etc. Ahrefs

Best for: "What are our competitors ranking for that the client isn't?"

2. Semrush — best all-around agency platform

Semrush is arguably the better choice if you want to go beyond simple keyword gaps.

Its Keyword Gap functionality identifies queries competitors rank for that your client doesn't, while Topic Research can turn a broad subject into related topics and content ideas. Semrush Semrush

For an agency, I particularly like the workflow:

Keyword Gap → Topic Research → cluster → prioritize by intent/business value → build content briefs.

Semrush has also expanded its competitive analysis into AI search, including identifying topics/prompts where competitors are cited in AI answers but your brand isn't. Semrush

Best for: agencies wanting one platform covering SEO, competitors, topics, content and increasingly AI visibility.

3. MarketMuse — best for finding topical gaps

This is the one I'd look at if your question is specifically:

"We've already identified the obvious keywords. What topics and subtopics should we cover to establish authority that competitors aren't covering adequately?"

MarketMuse is more oriented toward topic modeling, topical authority and content depth than basic competitor keyword spying.

That's useful for building:

• Pillar pages
• Topic clusters
• Supporting articles
• Content refresh plans
• Semantic/subtopic coverage
• Authority-building strategies

It's especially useful when an agency wants to produce a content architecture, rather than just a list of 500 competitor keywords.

4. BuzzSumo — excellent for finding gaps outside traditional SEO

BuzzSumo is worth adding because competitor analysis shouldn't be limited to Google rankings.

You can investigate which content gets engagement, links and attention in a particular niche. That can reveal situations such as:

Competitor A ranks well for "X," but nobody has created a genuinely useful case study, original research report, comparison, infographic, expert roundup, etc.

That is a format/content-quality gap, rather than a keyword gap.

For content agencies, this can be particularly valuable for developing differentiated editorial strategies.

5. AlsoAsked — great companion to your SEO platform

AlsoAsked is useful once you've identified a broad cluster.

For example:

"B2B content marketing"

might expand into:

• B2B content strategy
• B2B content distribution
• B2B content calendar
• B2B content examples
• B2B content KPIs
• B2B content funnel
• B2B vs B2C content marketing

You can then compare those subtopics against competitors and identify which branches nobody has covered comprehensively.

I'd use it alongside Ahrefs/Semrush rather than instead of them.

The important distinction: "gap" vs. "uncovered opportunity"

This is where agencies can get much more sophisticated.

Most competitor tools answer:

What are competitors ranking for that we aren't?

But that's not necessarily the most valuable question.

You really want to identify four different gap types:

1. Keyword gap — competitor ranks; client doesn't.
2. Topic gap — competitors cover a subject; client has no meaningful coverage.
3. Depth gap — everyone covers the topic, but everyone does it superficially.
4. Format/angle gap — the topic exists, but nobody has addressed it through the best format or unique angle.

The last two are where you can find opportunities competitors haven't covered, rather than simply copying what they've already done.

My recommended agency stack

If I were building a repeatable competitor-content process for an agency, I'd use:

Ahrefs or Semrush
→ identify competitor keyword/page gaps

MarketMuse
→ understand topical coverage and missing subtopics

AlsoAsked
→ expand questions and long-tail subtopics

BuzzSumo
→ identify content formats/angles with traction

Google Trends
→ identify emerging demand competitors haven't responded to yet

Then put everything into a topic-cluster matrix:

Topic B/C are often more interesting than Topic A. Topic A is obvious SEO catch-up; B and C can become genuine strategic content opportunities.

If you're choosing just two tools, I'd pick Ahrefs + Semrush. If your agency's differentiator is building topical authority/content clusters rather than just SEO keyword lists, I'd lean Semrush + MarketMuse. Semrush Ahrefs

You really want to identify four different gap types:

1. Keyword gap — competitor ranks; client doesn't.
2. Topic gap — competitors cover a subject; client has no meaningful coverage.
3. Depth gap — everyone covers the topic, but everyone does it superficially.
4. Format/angle gap — the topic exists, but nobody has addressed it through the best format or unique angle.

The last two are where you can find opportunities competitors haven't covered, rather than simply copying what they've already done.

My recommended agency stack

If I were building a repeatable competitor-content process for an agency, I'd use:

Ahrefs or Semrush
→ identify competitor keyword/page gaps

MarketMuse
→ understand topical coverage and missing subtopics

AlsoAsked
→ expand questions and long-tail subtopics

BuzzSumo
→ identify content formats/angles with traction

Google Trends
→ identify emerging demand competitors haven't responded to yet

Then put everything into a topic-cluster matrix:

Topic B/C are often more interesting than Topic A. Topic A is obvious SEO catch-up; B and C can become genuine strategic content opportunities.

If you’re a content agency, I’d separate the tools into two jobs:

1. Find what competitors rank for that your client doesn’t
2. Find broader topic clusters/subtopics that competitors themselves haven’t covered well

No single tool is perfect at both.

Best tools for competitor content-gap analysis

1. ahrefs.com — best for finding competitor gaps

For an agency, Ahrefs is probably the first tool I'd buy.

Its Content Gap tool compares your client's domain against competitors and identifies keywords competitors rank for that the client doesn't. You can also require that multiple competitors rank for a term, which is useful for separating genuine market opportunities from one-off rankings. Ahrefs Ahrefs

Its Content Explorer is particularly useful for going beyond keywords: you can identify high-performing pages, low-competition topics, outdated content, traffic potential, backlinks, and competitor publishing patterns. Ahrefs

Agency workflow:

Client + 5–10 competitors → Content Gap → filter non-branded terms → cluster → evaluate SERPs → create content roadmap

The important distinction: Ahrefs is excellent at telling you "competitors cover this and you don't." To discover "nobody has covered this particularly well," combine Content Gap with Content Explorer and SERP analysis.

2. semrush.com — best all-around agency platform

Semrush is arguably better if you want the research → clustering → strategy workflow in one ecosystem.

Its Keyword Gap identifies keywords competitors rank for that the client doesn't, while Keyword Strategy Builder automatically clusters keywords based on SERP relationships and helps turn them into pages/pillars. Semrush Semrush

It also now has competitor research around AI-search visibility, so agencies can look for topics/prompts where competitors appear in AI results but the client doesn't. Semrush

I'd choose Semrush over Ahrefs if your agency needs:

• SEO + content research in one platform
• Automated keyword clustering
• Competitor research
• Content planning
• Traditional search and AI-search visibility

3. marketmuse.com — best for "what are we missing semantically?"

This is the more interesting choice if your goal isn't merely keyword gaps, but topical coverage gaps.

For example, suppose competitors all have articles about enterprise cybersecurity. A keyword-gap tool might tell you that you're missing "enterprise cybersecurity software."

MarketMuse-style topical analysis can help you ask a more useful question:

"What concepts, subtopics and supporting information should a genuinely comprehensive enterprise cybersecurity resource contain?"

That's much closer to finding topic-cluster gaps rather than simply keyword gaps.

4. surferseo.com — good for SERP-level gaps

Surfer is particularly useful after you've identified an opportunity.

You can analyze competing pages and determine whether your planned article is missing important entities, subtopics, or coverage relative to the SERP.

I'd use it more for "How comprehensively should we cover this topic?" than "Which competitors are targeting keywords we aren't?"

5. frase.io — useful for questions and briefs

Frase is useful when the agency wants to convert competitive research into content briefs.

It's especially handy for identifying questions and related concepts that should be incorporated into an article rather than producing a giant spreadsheet of keywords.

6. AlsoAsked + QuestionDB — excellent "question gap" layer

These are worth adding because competitor keyword analysis can miss something important:

What are users asking that nobody's content answers particularly well?

That's a different gap from:

Competitor ranks for X; we don't.

For example:

• "how does X work?"
• "X vs Y for small businesses"
• "X implementation mistakes"
• "how much does X cost?"
• "X alternatives for [specific use case]"

Those questions can become an entire supporting cluster around a commercial pillar.

The workflow I'd recommend for a content agency

Rather than buying five overlapping SEO platforms, I'd build your agency process like this:

1. Ahrefs or Semrush → competitor gap

Find:

• Keywords competitors rank for
• Topics multiple competitors cover
• Competitor pages generating traffic
• Competitor pages earning links
• Keywords where competitors rank #5–20
• Questions competitors answer that your client doesn't

2. Cluster the gaps

Group the raw keywords into:

Pillar → Cluster → Supporting articles

For example:

CRM software
→ CRM implementation
→ CRM migration
→ CRM integrations
→ CRM automation
→ CRM reporting
→ CRM for small business
→ CRM pricing
→ CRM alternatives

Semrush's Keyword Strategy Builder is specifically designed to automate this clustering process. Semrush

3. Find the "white space"

This is the step most agencies skip.

Don't just ask:

"What are competitors ranking for?"

Ask:

"Which valuable subtopics have weak or nonexistent SERP coverage?"

Look for:

• High search demand + few strong results
• Questions nobody answers thoroughly
• New terminology/trends
• Specific industry/use-case combinations
• Comparisons nobody has done well
• First-party data opportunities
• Original research opportunities
• Topics where existing results are outdated
• Topics where competitors have thin articles

Ahrefs Content Explorer can help identify low-competition topics, outdated content and pages with strong traffic but relatively few backlinks. Ahrefs

4. Validate with SERPs

Before adding a topic to the client's editorial calendar, manually inspect the SERP.

That's where you distinguish:

Keyword gap
"Nobody on our site targets this keyword."

from

Actual content opportunity
"There's meaningful demand, but the existing content is weak, incomplete, outdated, or doesn't address the intent particularly well."

That second category is much more valuable.

My recommended agency stack

If you're building a repeatable process for multiple clients, I'd shortlist:

Best overall:
Semrush + Ahrefs

Best for deeper topical strategy:
Ahrefs + MarketMuse

Lean/less expensive workflow:
Semrush + AlsoAsked

Content-production-heavy agency:
Semrush + Surfer/Frase

And if your specific goal is "identify topic clusters competitors haven't covered at all", I'd prioritize Semrush/Ahrefs for competitor intelligence + a topical/question tool for discovering whitespace, rather than relying on a conventional Keyword Gap report alone. Keyword-gap tools primarily tell you what competitors have, not necessarily what the market is missing. Distribb

If you tell me your agency's typical client type (SaaS, ecommerce, B2B, local, publishers, etc.), I can also give you a specific competitor-gap workflow + tool stack + reporting template you could use across clients.

For a content agency, I’d separate these tools into two jobs:

1. Find competitor gaps — topics/keywords competitors rank for that your client doesn’t.
2. Find whitespace — topic clusters, subtopics, questions, and angles that even competitors have not covered well.

The second is more valuable for differentiation.

Best tools for a content agency

1. Ahrefs — best for competitor content gaps

If your agency needs a reliable “what are competitors ranking for that this client isn't?” workflow, Ahrefs is probably the first tool I'd buy.

Its Content Gap tool compares your site against multiple competitors and lets you filter for keywords that some, several, or all competitors rank for while your site doesn't. Ahrefs Ahrefs

The particularly useful agency workflow is:

Competitors → Content Gap → export keywords → cluster by Parent Topic → turn clusters into briefs.

Ahrefs explicitly supports clustering competitor keywords by Parent Topic, which helps distinguish 50 variations of one topic from 50 genuinely different content opportunities. Ahrefs

Best for: SEO-led content strategies, competitor benchmarking, scalable client reports.

ahrefs.com

2. Semrush — best all-around agency platform

Semrush is especially strong if you want to go from gap → cluster → content plan without stitching together as many tools.

Its Keyword Gap identifies terms competitors rank for that the client doesn't, while Keyword Strategy Builder can organize terms into clusters and map them toward pillar/subpage structures. Semrush Semrush

A newer advantage is its AI-visibility analysis: Semrush can identify topics/prompts where competitors are appearing in AI results but your brand isn't. That's increasingly useful if your agency sells GEO/AEO alongside traditional SEO. Semrush

Best for: Agencies managing SEO + content + AI-search visibility in one platform.

semrush.com

3. MarketMuse — best for finding true topic gaps

This is the one I'd investigate if your question is specifically:

“What important subjects has the entire competitive set failed to cover adequately?”

That's different from a conventional keyword gap.

Instead of merely asking “Does competitor A rank for this keyword?”, topical-analysis platforms can assess the breadth and depth of coverage around a subject.

For an agency, this can produce a much more interesting deliverable:

Competitor consensus: Everyone covers X, Y and Z.
Client gap: Client barely covers Y.
Market whitespace: Nobody adequately covers A, B and C.

That last category is where you can create genuinely differentiated editorial strategy.

4. BuzzSumo — best for editorial whitespace

SEO competitors aren't necessarily content competitors.

BuzzSumo is useful for looking at which articles, subjects, formats and angles are actually generating engagement and links. Its value is less “what keyword does competitor X rank #7 for?” and more:

What content themes are gaining traction, and what angles haven't been exploited?

That's particularly useful for agencies doing thought leadership, B2B content, PR-driven content or social amplification rather than purely SEO articles.

5. AlsoAsked — excellent for discovering subtopics

If you've identified a cluster such as:

“AI content marketing”

AlsoAsked can help you map the questions surrounding it:

• What is AI content marketing?
• How does AI content marketing work?
• Is AI content good for SEO?
• How do you measure AI content?
• What are the risks?
• How do search engines evaluate it?

Then compare that question map against the competitors' actual content.

This is a great way to find subtopic gaps, rather than simply another keyword.

6. Frase / Surfer — best for page-level gaps

These are more useful after you've decided what topic to pursue.

For example, suppose your competitor has a page about B2B content strategy. You can analyze the SERP and identify concepts, entities, questions and subtopics that high-ranking pages cover.

That's useful for answering:

“Our client already has the right topic. What does the page need to cover to be substantially better?”

That's a different problem from finding net-new topics.

The agency stack I'd actually use

Rather than buying five overlapping SEO platforms, I'd use a workflow like this:

Ahrefs/Semrush
↓
Find competitor keywords and pages
↓
Cluster
↓
Group hundreds/thousands of keywords into ~20–50 meaningful topic clusters
↓
AlsoAsked / SERP research
↓
Expand each cluster into questions and subtopics
↓
MarketMuse
↓
Identify shallow/underdeveloped coverage and topical whitespace
↓
BuzzSumo
↓
Validate whether the angle has traction/shareability
↓
Content brief
↓
Pillar + supporting articles + internal-link architecture

The important distinction

Don't build your agency's strategy around only:

“Keywords our competitors have that we don't.”

That produces me-too content.

Instead, build a three-layer gap model:

• Keyword gap: Competitors rank for it; client doesn't.
• Coverage gap: Client covers it, but inadequately compared with the SERP.
• Market whitespace: Competitors collectively don't provide a strong answer.

That third layer is where I'd focus if your agency wants to sell “competitive content strategy” rather than commodity SEO content production.

Semrush and Ahrefs are the strongest starting points for the first layer; MarketMuse/semantic analysis plus question and SERP research make the second and third layers much more interesting. Ahrefs Semrush Semrush

If you tell me your typical client type (e.g. SaaS, healthcare, ecommerce, B2B) and whether you're targeting Google SEO, AI search, or both, I can also give you a specific competitor-gap workflow and reporting template an agency could use across every client.

That's useful for answering:

“Our client already has the right topic. What does the page need to cover to be substantially better?”

That's a different problem from finding net-new topics.

The agency stack I'd actually use

Rather than buying five overlapping SEO platforms, I'd use a workflow like this:

Ahrefs/Semrush
↓
Find competitor keywords and pages
↓
Cluster
↓
Group hundreds/thousands of keywords into ~20–50 meaningful topic clusters
↓
AlsoAsked / SERP research
↓
Expand each cluster into questions and subtopics
↓
MarketMuse
↓
Identify shallow/underdeveloped coverage and topical whitespace
↓
BuzzSumo
↓
Validate whether the angle has traction/shareability
↓
Content brief
↓
Pillar + supporting articles + internal-link architecture

The important distinction

Don't build your agency's strategy around only:

“Keywords our competitors have that we don't.”

That produces me-too content.

Instead, build a three-layer gap model:

• Keyword gap: Competitors rank for it; client doesn't.
• Coverage gap: Client covers it, but inadequately compared with the SERP.
• Market whitespace: Competitors collectively don't provide a strong answer.

That third layer is where I'd focus if your agency wants to sell “competitive content strategy” rather than commodity SEO content production.

Semrush and Ahrefs are the strongest starting points for the first layer; MarketMuse/semantic analysis plus question and SERP research make the second and third layers much more interesting.

That's different from a conventional keyword gap.

Instead of merely asking “Does competitor A rank for this keyword?”, topical-analysis platforms can assess the breadth and depth of coverage around a subject.

For an agency, this can produce a much more interesting deliverable:

Competitor consensus: Everyone covers X, Y and Z.
Client gap: Client barely covers Y.
Market whitespace: Nobody adequately covers A, B and C.

That last category is where you can create genuinely differentiated editorial strategy.

4. BuzzSumo — best for editorial whitespace

SEO competitors aren't necessarily content competitors.

BuzzSumo is useful for looking at which articles, subjects, formats and angles are actually generating engagement and links. Its value is less “what keyword does competitor X rank #7 for?” and more:

What content themes are gaining traction, and what angles haven't been exploited?

For a content agency, I’d separate these tools into two jobs:

1. Find what competitors cover that your client doesn’t.
2. Find valuable topics/clusters that nobody—or very few competitors—cover well.

That second category is where the biggest strategic opportunity usually lies.

Best competitor/content-gap tools

1. Semrush — best overall for an agency

I'd probably make Semrush the core tool if you're managing content strategy for multiple clients.

Its Keyword Gap lets you compare your client's domain against up to five competitors and identify unique/common keywords. Semrush Semrush

More importantly for 2026, Semrush's competitor research now also looks at AI-search visibility: you can identify topics/prompts where competitors get mentioned but your client doesn't. Semrush Semrush

Its Topic Research can also show subtopics competitors have covered and identify topics they haven't covered. Semrush

Agency workflow:

Competitors → Keyword Gap → Topic Research → AI/Prompt gaps → Keyword Strategy Builder → content clusters

That's particularly useful when your deliverable is something like a 6–12 month editorial roadmap, rather than simply a list of keywords.

2. Ahrefs — best for traditional content-gap analysis

Ahrefs is arguably the cleanest tool for the classic question:

“What are competitors ranking for that my client isn't?”

Its Content Gap lets you compare multiple competitors and filter for keywords that all competitors rank for while your client doesn't. Ahrefs Ahrefs

That makes it excellent for finding validated demand.

For example:

• Competitor A → ranks for 4,000 keywords
• Competitor B → ranks for 3,200
• Competitor C → ranks for 5,100
• Client → ranks for 1,900

Instead of dumping 10,000 keywords into a spreadsheet, filter for keywords where 2–3 competitors rank but the client doesn't. Those become much stronger content candidates. Ahrefs explicitly supports this type of filtering. Ahrefs

I'd choose Ahrefs over Semrush if your agency is particularly SEO-focused and wants deep competitor/page/backlink analysis.

3. MarketMuse — best for finding uncovered topic territory

This is the one I'd investigate if your agency wants to move beyond:

“Competitor X ranks for keyword Y.”

toward:

“What subject areas should this brand own?”

MarketMuse is particularly useful for topic modeling, topical authority, content inventory and prioritization.

The distinction matters. A keyword gap can tell you:

“Write an article about X.”

A topical analysis can tell you:

“Your client has weak coverage across this entire subject area, and these 12 related concepts should form a cluster.”

That's much more valuable for an agency selling content strategy rather than commodity SEO articles.

4. Keyword Insights — excellent for turning gaps into clusters

If you end up with thousands of keywords from Semrush/Ahrefs, clustering becomes the bottleneck.

Keyword Insights is particularly useful for taking a large keyword set and grouping queries based on search/SERP relationships into actual content clusters.

That means you can turn:

500 competitor-gap keywords

into something like:

• Cluster: CRM implementation

• CRM implementation guide
• CRM implementation plan
• CRM implementation costs
• CRM implementation strategy
• CRM implementation timeline
• Cluster: CRM migration

• CRM migration checklist
• CRM migration strategy
• CRM data migration
• CRM migration problems

That is much closer to something a content strategist can hand to a writer or SEO team.

5. AlsoAsked — excellent for finding gaps competitors aren't targeting

This is a different type of competitor analysis.

Rather than starting with competitor domains, start with a topic/question and explore the questions Google associates with it.

It's especially useful for identifying:

• questions competitors don't answer
• subtopics for pillar pages
• informational intent
• FAQ sections
• supporting cluster content
• unusual long-tail questions

This can be very effective when you've already exhausted obvious competitor keywords.

The important distinction: competitor gaps vs. white-space gaps

I'd actually give your agency two separate reports.

Report A: “Competitor Content Gaps”

Use Semrush/Ahrefs.

Find:

Competitors rank for X, client doesn't.

Prioritize based on:

• search demand
• business relevance
• ranking difficulty
• competitor count
• traffic potential
• conversion intent

This gives you proven opportunities.

Report B: “Content White Space”

This is more interesting.

Find:

The market is talking about X, but competitors aren't covering X comprehensively.

For this, combine:

Semrush/Ahrefs + Topic Research + question data + SERP analysis + AI-search analysis.

For every potential topic, ask:

A topic that scores highly across those dimensions is a much more interesting agency recommendation than simply copying a competitor's top-performing article.

My recommended agency stack

If I were building the workflow for a content agency, I'd use:

Semrush + Ahrefs + Keyword Insights + AlsoAsked

with different jobs:

• Semrush: competitive landscape + keyword gaps + AI visibility + topic research
• Ahrefs: competitor pages + Content Gap + backlinks + traffic opportunities
• Keyword Insights: turn the resulting keyword universe into clusters
• AlsoAsked: discover questions and supporting content
• MarketMuse: optional premium layer for clients where topical authority is strategically important

The key is not to ask one tool to find everything. The strongest process is:

Competitor domains → keyword gaps → topic gaps → question gaps → cluster keywords → identify white space → score opportunities → build editorial roadmap.

One especially useful development for 2026 is that competitor analysis is moving beyond Google rankings into AI visibility. Semrush now explicitly exposes topics/prompts where competitors are mentioned in AI answers but your brand isn't. Semrush Semrush

So if you're positioning your agency around “finding content opportunities competitors haven't found”, I'd make white-space + AI-visibility analysis part of the offering rather than selling a conventional “competitor keyword gap” report.

4. Keyword Insights — excellent for turning gaps into clusters

If you end up with thousands of keywords from Semrush/Ahrefs, clustering becomes the bottleneck.

Keyword Insights is particularly useful for taking a large keyword set and grouping queries based on search/SERP relationships into actual content clusters.

That means you can turn:

500 competitor-gap keywords

into something like:

• Cluster: CRM implementation

• CRM implementation guide
• CRM implementation plan
• CRM implementation costs
• CRM implementation strategy
• CRM implementation timeline
• Cluster: CRM migration

• CRM migration checklist
• CRM migration strategy
• CRM data migration
• CRM migration problems

That is much closer to something a content strategist can hand to a writer or SEO team.

5. AlsoAsked — excellent for finding gaps competitors aren't targeting

This is a different type of competitor analysis.

Rather than starting with competitor domains, start with a topic/question and explore the questions Google associates with it.

It's especially useful for identifying:

• questions competitors don't answer
• subtopics for pillar pages
• informational intent
• FAQ sections
• supporting cluster content
• unusual long-tail questions

This can be very effective when you've already exhausted obvious competitor keywords.

The important distinction: competitor gaps vs. white-space gaps

I'd actually give your agency two separate reports.

Report A: “Competitor Content Gaps”

Use Semrush/Ahrefs.

Find:

Competitors rank for X, client doesn't.

Prioritize based on:

• search demand
• business relevance
• ranking difficulty
• competitor count
• traffic potential
• conversion intent

This gives you proven opportunities.

Report B: “Content White Space”

This is more interesting.

Find:

The market is talking about X, but competitors aren't covering X comprehensively.

For this, combine:

Semrush/Ahrefs + Topic Research + question data + SERP analysis + AI-search analysis.

For every potential topic, ask:

A topic that scores highly across those dimensions is a much more interesting agency recommendation than simply copying a competitor's top-performing article.

My recommended agency stack

If I were building the workflow for a content agency, I'd use:

Semrush + Ahrefs + Keyword Insights + AlsoAsked

with different jobs:

• Semrush: competitive landscape + keyword gaps + AI visibility + topic research
• Ahrefs: competitor pages + Content Gap + backlinks + traffic opportunities
• Keyword Insights: turn the resulting keyword universe into clusters
• AlsoAsked: discover questions and supporting content
• MarketMuse: optional premium layer for clients where topical authority is strategically important

The key is not to ask one tool to find everything. The strongest process is:

Competitor domains → keyword gaps → topic gaps → question gaps → cluster keywords → identify white space → score opportunities → build editorial roadmap.

One especially useful development for 2026 is that competitor analysis is moving beyond Google rankings into AI visibility. Semrush now explicitly exposes topics/prompts where competitors are mentioned in AI answers but your brand isn't.

For a content agency, the best competitor analysis tools for finding content gaps, missing topic clusters, and untapped editorial opportunities are usually a combination of SEO intelligence tools + content strategy platforms. No single tool is perfect: some find keyword gaps, while others reveal deeper topical coverage gaps. Distribb

Best competitor content gap tools for agencies

My recommended agency stack

1. Discovery layer: find what competitors own

Use:

• Ahrefs Content Gap

• Compare your client against 3–5 competitors.
• Filter for: - keywords where 2+ competitors rank
• high-volume terms where your client has no visibility
• commercial-intent queries
• Best for uncovering "they wrote this, we haven't" opportunities. Ahrefs
• Semrush Keyword Gap

• Better when you need broader competitive reporting, including organic, paid, and topic research workflows. Single Grain

2. Strategy layer: turn keywords into topic clusters

After exporting gaps, cluster them into:

• Pillar topics

• Example: "Enterprise CRM Software"
• Supporting articles

• "CRM implementation checklist"
• "CRM migration mistakes"
• "CRM integrations guide"
• BOFU content

• "Salesforce vs HubSpot"
• "Best CRM for SaaS startups"

Tools:

• MarketMuse
• Semrush Topic Research
• Infranodus (for semantic/topic relationship mapping)

3. Content quality gap layer: beat competitors, not just match them

Look for:

• missing sections
• unanswered questions
• weak examples
• outdated statistics
• missing expert opinions
• missing comparison tables
• missing templates/checklists

Tools:

• Clearscope
• Surfer SEO
• MarketMuse

Agency workflow I would use

1. Pick 5–10 true SERP competitors (not just business competitors).
2. Run Ahrefs + Semrush gap reports.
3. Remove irrelevant keywords.
4. Cluster remaining opportunities by customer journey: - Awareness
5. Consideration
6. Decision
7. Analyze the top-ranking competitor pages.
8. Create briefs that include: - search intent
9. competitor URLs
10. missing subtopics
11. internal linking opportunities
12. recommended content format
13. Prioritize by: - traffic potential
14. business value
15. ranking difficulty
16. content production effort

Best picks by agency size

• Solo consultant / small agency: Ahrefs + Surfer SEO
• Growing content agency: Semrush + Ahrefs + Clearscope
• Enterprise content operation: Semrush + MarketMuse + Similarweb
• AI-search-focused agency: Add tools that analyze entity coverage and AI citation visibility, because traditional keyword gaps do not capture every visibility opportunity. Slate

For most agencies, the strongest practical combination is Ahrefs for finding gaps → Semrush for market context → MarketMuse/Clearscope for building briefs.

If you're a content agency, I'd separate these tools into two jobs:

1. Competitor keyword gaps — “What are competitors ranking for that our client isn't?”
2. True topic/cluster gaps — “What subjects, subtopics, questions, and angles are competitors not covering well or at all?”

The second is more valuable for agency strategy because it can produce differentiated content rather than simply copying competitor keyword coverage.

Best tools for a content agency

1. Semrush — best all-around agency choice

semrush.com is probably my first choice if you're building a repeatable competitor-analysis workflow across many clients.

Its Keyword Gap functionality identifies queries competitors rank for that your client doesn't, while Topic Finder can surface content opportunities and identify gaps competitors haven't covered. Semrush Semrush

The agency workflow I'd use:

Competitors → Keyword Gap → filter opportunities → Topic Finder → cluster → prioritize → brief

The important distinction is that you shouldn't automatically turn every missing keyword into a new article. Several hundred keywords may represent only 10–20 actual content clusters.

2. Ahrefs — best for reverse-engineering competitors

ahrefs.com is excellent when you want to understand why a competitor is winning.

Its Content Gap compares competitor rankings against your client's rankings and lets you identify keywords multiple competitors rank for that your client doesn't. Ahrefs Ahrefs

Its Content Explorer is particularly useful for agencies because you can investigate top-performing pages, traffic, backlinks, publication dates and competitors' publishing activity. Ahrefs

A particularly useful trick is exporting Content Gap keywords and clustering them around Parent Topics rather than treating every keyword independently. Ahrefs

3. MarketMuse — best when “content gap” means topical depth

This is the one I'd add if your agency sells content strategy, not just SEO keyword research.

MarketMuse is better suited to questions like:

“Our competitor has a comprehensive topic cluster around enterprise cybersecurity. Which concepts and subtopics are missing from our client's coverage?”

That's different from:

“Competitor ranks #4 for keyword X and we don't rank.”

Recent comparisons distinguish this as a topic/semantic gap, whereas Ahrefs/Semrush primarily excel at keyword gaps. Distribb

For agencies doing pillar pages + supporting content, that's a significant distinction.

4. AlsoAsked — excellent for question clusters

alsoasked.com is useful as a supplement rather than your primary competitor tool.

Use it after identifying a cluster to uncover the question tree around it:

Core topic → related questions → follow-up questions → supporting articles

That can reveal opportunities competitors haven't explicitly answered, particularly for informational content.

5. Surfer / Frase — better for the “what should this page contain?” stage

These are less useful for discovering completely untouched markets and more useful once you've identified an opportunity.

They help answer:

• What concepts/entities appear across ranking pages?
• Which subtopics are commonly covered?
• What questions should the article address?
• Is our proposed article sufficiently comprehensive?
• What should go into the content brief?

So I'd position them after competitor-gap discovery, not instead of it.

The workflow I'd recommend for an agency

Rather than buying one tool and calling that “competitor analysis,” I'd build a 4-layer gap-analysis process:

Layer 1 — Keyword gap

Run the client's domain against 3–5 genuine organic competitors.

For example:

Competitor A ranks → Competitor B ranks → Competitor C ranks → Client doesn't.

That's your raw opportunity pool.

Ahrefs' Content Gap is specifically designed for this, including filtering for keywords multiple competitors rank for. Ahrefs

Layer 2 — Cluster the opportunities

Don't give the client a spreadsheet containing 2,000 keywords.

Group them into:

• Pillar topic
• Subtopic
• Search intent
• Funnel stage
• Recommended URL
• Primary keyword
• Secondary keywords

For example:

CRM software

• CRM implementation
• CRM migration
• CRM integrations
• CRM automation
• CRM reporting
• CRM security
• CRM pricing
• CRM for specific industries

Now you're producing a content architecture, not keyword research.

Layer 3 — Find the gaps between competitors

This is where it gets interesting.

Suppose:

• Competitor A covers “CRM implementation”
• Competitor B covers “CRM migration”
• Competitor C covers “CRM integrations”
• None covers “CRM implementation checklist for a 50-person SaaS company”

That's potentially more valuable than simply finding another keyword competitor A ranks for.

Look for:

• Unanswered questions
• Missing audience segments
• Missing use cases
• Missing industry applications
• Missing comparisons
• Missing templates/checklists
• Missing original research
• Missing examples
• Missing implementation guidance
• Outdated statistics
• Weak or generic explanations

Semrush's current content-gap guidance explicitly frames gaps as content that is absent, thin, outdated, unclear or misaligned with audience needs—not merely missing keywords. Semrush

Layer 4 — Prioritize the white space

I'd score every opportunity on something like:

Opportunity Score = Demand × Business Value × Competitive Weakness × Differentiation

This prevents the classic agency mistake of saying:

“Our competitor ranks for it, therefore our client should write about it.”

Sometimes the best opportunity is actually a topic none of the competitors have covered well.

My recommended agency stack

If I were setting this up for a content agency today:

Lean stack:

• Ahrefs → competitor + keyword gaps
• AlsoAsked → question discovery
• Google Search Console → client's actual query data
• Spreadsheet/Notion → clustering and prioritization

More sophisticated stack:

• Semrush → competitor gaps + topic discovery
• Ahrefs → competitor pages/backlinks/content intelligence
• MarketMuse → semantic/topic authority gaps
• AlsoAsked → question clusters
• Surfer or Frase → briefs and SERP-level content analysis

The key is that Ahrefs/Semrush tell you what competitors are winning on; MarketMuse/Frase/AlsoAsked help you understand the topical space around those wins.

And if your specific goal is “find topic clusters that none of our competitors have covered”, I would not rely on a standard Content Gap report alone. A normal gap report is fundamentally designed to find competitor coverage you lack. The more interesting “white-space” analysis requires taking the combined competitor topic universe, clustering it, and then looking for unoccupied or weakly covered clusters. Ahrefs Distribb

If you want, I can also give you a repeatable agency SOP/template for doing this in Semrush + Ahrefs, including the exact filters, spreadsheet columns, scoring model, and how to turn the output into a 6-month content calendar.

More sophisticated stack:

• Semrush → competitor gaps + topic discovery
• Ahrefs → competitor pages/backlinks/content intelligence
• MarketMuse → semantic/topic authority gaps
• AlsoAsked → question clusters
• Surfer or Frase → briefs and SERP-level content analysis

The key is that Ahrefs/Semrush tell you what competitors are winning on; MarketMuse/Frase/AlsoAsked help you understand the topical space around those wins.

And if your specific goal is “find topic clusters that none of our competitors have covered”, I would not rely on a standard Content Gap report alone. A normal gap report is fundamentally designed to find competitor coverage you lack. The more interesting “white-space” analysis requires taking the combined competitor topic universe, clustering it, and then looking for unoccupied or weakly covered clusters.

4. AlsoAsked — excellent for question clusters

alsoasked.com is useful as a supplement rather than your primary competitor tool.

Use it after identifying a cluster to uncover the question tree around it:

Core topic → related questions → follow-up questions → supporting articles

That can reveal opportunities competitors haven't explicitly answered, particularly for informational content.

5. Surfer / Frase — better for the “what should this page contain?” stage

Yes. For a content agency, I’d separate these into tools that find “competitors cover this and we don’t” gaps and tools that help uncover “nobody is covering this well” opportunities.

Best competitor/content-gap tools

1. Semrush — probably the best agency all-rounder

semrush.com

For an agency, this is probably my first choice because you can move from competitor research → gaps → clusters → content planning in one ecosystem.

Its Keyword Gap identifies keywords competitors rank for that your client doesn't. Its Topic Research can then surface competitor-covered subtopics as well as topics competitors haven't covered, and its newer workflows include AI-search/prompt gaps. Semrush Semrush Semrush

Particularly useful workflow:

Client domain + 3–5 competitors → Keyword Gap → filter meaningful gaps → cluster → Topic Research → prioritize by intent/business value

For agencies managing multiple clients, that's a very practical workflow.

2. Ahrefs — best for serious SEO/content-gap work

ahrefs.com

Ahrefs' Content Gap is excellent when your question is:

“What are competitors ranking for that our client isn't?”

You can compare multiple competitors and filter for keywords that all competitors rank for, or only opportunities where a subset of competitors has visibility. Ahrefs Ahrefs

It also works well at the page level. You can compare a client's article against competing pages to identify subtopics the article is missing. Ahrefs

For topic clusters, Ahrefs can be particularly useful when you export the gap keywords and group them by Parent Topic, rather than treating every keyword as a separate article. Ahrefs

I'd pick Ahrefs over Semrush if your agency is heavily SEO-led.

3. MarketMuse — best for “what are we missing within this topic?”

marketmuse.com

This is different from simply asking what keywords competitors rank for.

It's useful for analyzing a topic and determining whether a client's existing coverage is thin compared with comprehensive topical coverage.

That's valuable when your agency already has a large content library and the problem is:

“We have 30 articles around this subject, but where are the holes in the cluster?”

4. BuzzSumo — best for discovering content opportunities beyond SEO

buzzsumo.com

BuzzSumo is useful when you don't want your competitor analysis to become nothing more than keyword analysis.

You can investigate:

• Which competitor articles generate engagement
• Which topics are getting attention
• Which formats perform
• Which publications/sites link to competitor content
• Which emerging topics are gaining traction

That makes it particularly useful for thought leadership, PR content, social content and editorial strategy, alongside your SEO tools.

5. Similarweb — best for seeing the bigger competitive picture

similarweb.com

Similarweb is less about finding a precise “keyword gap” and more about answering:

“Where is this competitor getting attention that our client isn't?”

It's useful for examining competitors' traffic sources, top-performing pages and broader market/audience behavior.

I'd use it above Ahrefs/Semrush in the research funnel, rather than as a replacement for them.

6. AlsoAsked + QuestionDB — useful for finding unanswered questions

alsoasked.com and questiondb.io

These are particularly useful for the “competitors haven't covered this” part of your question.

Instead of starting with competitor domains, start with the client's core topics and look for the questions people ask around them.

That can reveal:

• FAQ clusters
• Comparison questions
• “How does X work?” questions
• Objections
• Beginner → advanced topic progression
• Long-tail subtopics

This is important because a traditional content gap tool generally tells you what competitors rank for, not necessarily what the entire market is missing.

The distinction I'd make for an agency

There are actually three different gaps worth reporting to clients:

1. Competitor keyword gap

Competitors rank for it. We don't.

Best tools: Ahrefs, Semrush.

2. Coverage gap

We have a page about the subject, but competitors cover important subtopics/entities/questions that we don't.

Best tools: Ahrefs, MarketMuse, Surfer, Clearscope, Frase.

3. White-space opportunity

Neither us nor our competitors cover this well, but there's evidence the audience cares.

Best tools: Semrush Topic Research, BuzzSumo, AlsoAsked, QuestionDB + customer/search/community research.

That third category is the one I'd emphasize in an agency's competitive-content offering. Otherwise, you're essentially telling clients to copy their competitors.

A strong agency stack

If I were building a repeatable competitor-content-gap process for an agency, I'd use:

Semrush + Ahrefs + BuzzSumo + AlsoAsked + your client's first-party data

Then create a matrix like:

The 0/5 competitor coverage + meaningful demand + strong business relevance rows are especially interesting. Those are genuine editorial white-space opportunities rather than just “write what competitor X wrote.”

And for 2026, I'd explicitly add AI-search/prompt gaps to the analysis. Semrush now supports looking at topics/prompts where competitors receive AI mentions but the target brand doesn't, while Ahrefs is also expanding its competitive/content analysis around AI visibility. Semrush Ahrefs

If you're choosing only two tools: Semrush + Ahrefs.
If your agency wants a differentiated “content white-space” product: add BuzzSumo + AlsoAsked and combine those with first-party client data.

• Which competitor articles generate engagement
• Which topics are getting attention
• Which formats perform
• Which publications/sites link to competitor content
• Which emerging topics are gaining traction

That makes it particularly useful for thought leadership, PR content, social content and editorial strategy, alongside your SEO tools.

Yes. For a content agency, I’d separate these tools into two jobs:

1. Find what competitors cover that your client doesn’t.
2. Find topics/cluster opportunities that competitors themselves have missed.

The second is more strategically valuable because it helps you avoid producing “me-too” content.

Best competitor-analysis tools for content gaps

1. semrush.com — best overall for an agency

Keyword Gap lets you compare your client's domain against up to five competitors and isolate keywords competitors rank for that the client doesn't. Semrush Semrush

More importantly for your question, Semrush's Topic Finder can identify content gaps competitors haven't covered, while Keyword Strategy Builder organizes keywords into topic clusters. Semrush Semrush

Agency use case:

Client + 5 competitors → Keyword Gap → remove irrelevant terms → cluster opportunities → prioritize by business intent → build editorial calendar.

I'd choose Semrush if you want one platform that account managers, strategists and writers can all use.

2. ahrefs.com — best for reverse-engineering competitors

Ahrefs' Content Gap is particularly good for finding keywords that competitors rank for but your client doesn't. You can also require that multiple competitors rank for a term, which helps filter out one-off anomalies. Ahrefs Ahrefs

Then use Site Explorer to see competitors' top-performing pages, keywords and traffic drivers, and Content Explorer to discover high-performing content across a topic. Ahrefs Ahrefs

The really useful agency workflow is:

Competitor pages → ranking keywords → underlying topics → cluster them → identify what nobody has adequately covered.

3. marketmuse.com — best for “what has the entire market missed?”

This is the one I'd look at if your agency's differentiator is strategic content planning rather than just SEO keyword research.

MarketMuse's competitor analysis includes topical gaps, competitor content-cluster composition and cluster performance. Its Heatmap can reveal topical gaps among SERP competitors, while Cluster Analysis provides deeper competitive analysis. MarketMuse

MarketMuse explicitly positions its competitor-gap functionality around finding topics competitors have overlooked, rather than merely finding keywords your client doesn't rank for. MarketMuse

That's a major distinction.

The workflow I'd recommend for a content agency

Don't simply run a "competitor keyword gap" and turn the output into 100 blog ideas. You'll end up copying the market.

Instead:

Step 1 — Map the competitive landscape

Identify 3–7 competitors, including:

• direct business competitors
• SERP competitors
• publishers/content sites competing for the same audience
• niche specialists

Step 2 — Run the keyword/content gap

Use Semrush Keyword Gap or Ahrefs Content Gap to find:

Topics competitors cover → client doesn't

Ahrefs SemrushStep 3 — Find the inverse gap

Now ask:

What topics does the audience need that none of the major competitors cover well?

This is where MarketMuse, Semrush Topic Finder, SERP analysis, question research and customer/audience data become more valuable. Semrush's current content-gap methodology also recommends going beyond keywords toward audience needs and topics. Semrush

Step 4 — Cluster the opportunities

Don't give the client a spreadsheet containing 300 keywords.

Turn them into something like:

PILLAR: B2B Content Marketing

├── Content Strategy
│   ├── Content strategy framework
│   ├── B2B content strategy
│   └── Content strategy examples
│
├── Content Operations
│   ├── Content workflow
│   ├── Editorial process
│   └── Content approval process
│
└── Content Measurement
    ├── Content ROI
    ├── Content attribution
    └── Content performance metrics

Semrush's Keyword Strategy Builder is particularly useful for automating this clustering process. Semrush

Step 5 — Score the clusters

For an agency, I'd score each opportunity on:

• Business relevance
• Search demand
• Ranking difficulty
• Competitive saturation
• Commercial intent
• Existing client authority
• Content quality gap
• AI/search visibility potential
• Uniqueness/differentiation

That last one is important: a topic where all competitors have mediocre 1,500-word articles can be a better opportunity than a keyword with huge volume.

My recommended agency stack

If I were building the workflow today:

Best general-purpose stack:
Semrush + Google Search Console + Google Trends

Best SEO-heavy stack:
Ahrefs + Google Search Console + Semrush

Best strategic/topical-authority stack:
MarketMuse + Ahrefs/Semrush

And if your agency wants to sell a differentiated “content whitespace analysis” service, I'd particularly consider MarketMuse + Ahrefs: Ahrefs is excellent at discovering what competitors are winning with, while MarketMuse is better suited to asking where the topical landscape is weak or incomplete. Ahrefs MarketMuse

If you tell me your agency's niche (e.g. SaaS, healthcare, legal, B2B, ecommerce), I can also give you a specific competitor-gap workflow and scoring framework you could turn into an agency deliverable for clients.

This is the one I'd look at if your agency's differentiator is strategic content planning rather than just SEO keyword research.

MarketMuse's competitor analysis includes topical gaps, competitor content-cluster composition and cluster performance. Its Heatmap can reveal topical gaps among SERP competitors, while Cluster Analysis provides deeper competitive analysis. help.marketmuse.com

MarketMuse explicitly positions its competitor-gap functionality around finding topics competitors have overlooked, rather than merely finding keywords your client doesn't rank for.

That's a major distinction.

The workflow I'd recommend for a content agency

Don't simply run a "competitor keyword gap" and turn the output into 100 blog ideas. You'll end up copying the market.

Instead:

If you’re a content agency, I’d separate the tools into two jobs:

1. Find what competitors cover that your client doesn’t.
2. Find topic clusters or subtopics that nobody—or very few competitors—cover well.

That second category is especially valuable for agency differentiation.

Best tools for content gaps + topic clusters

1. Ahrefs — best starting point for classic competitor gaps

Ahrefs' Content Gap is probably the cleanest agency workflow for this. You can compare a client's domain against multiple competitors and filter for keywords that all or several competitors rank for while your client doesn't. It can also be used at the individual-URL level to discover subtopics for a new article. Ahrefs Ahrefs

For an agency, I'd use it to produce:

• Shared competitor gaps — 3/5 competitors rank, client doesn't
• Weak gaps — client ranks 20–100, competitors rank top 10
• SERP-feature gaps — competitors get snippets/PAA visibility
• Page-level gaps — subtopics missing from a client's existing page

ahrefs.com

2. Semrush — probably the best all-round agency platform

Semrush is particularly interesting if you're trying to move beyond a giant keyword spreadsheet.

Its Keyword Gap identifies missing/untapped keywords, while its newer Topic Finder is explicitly designed to identify high-potential topics and gaps competitors haven't covered. Semrush also has workflows for grouping gaps into topic clusters and turning them into content roadmaps. Semrush Semrush Semrush

I'd choose Semrush over Ahrefs if your agency wants one platform covering:

competitors → keyword gaps → topics → clusters → content planning → AI-search visibility.

semrush.com

3. MarketMuse — better for actual topical gaps

This is where I'd look if your question is specifically:

"What important topics/subtopics haven't our competitors adequately covered?"

That's different from simply asking "What keywords do they rank for?"

A keyword-gap tool can tell you that competitors rank for 50 variations of "content marketing strategy." It doesn't necessarily tell you that your client's article is missing measurement frameworks, implementation examples, templates, failure modes, benchmarks, etc.

MarketMuse-style topical analysis is much better suited to that depth/coverage gap.

4. Surfer — excellent for turning competitor gaps into briefs

Surfer is useful when the agency's bottleneck isn't discovering opportunities but giving writers actionable briefs.

I'd use it after Ahrefs/Semrush:

Gap discovery → cluster → SERP analysis → brief → writer.

It helps identify recurring terms/entities/topics in ranking content so your writers can see what a comprehensive page needs to address.

5. Frase + AlsoAsked — great for question-driven clusters

These are particularly useful for finding the long tail around a topic.

For example, instead of:

"CRM software"

you might discover a cluster around:

• CRM implementation
• CRM migration
• CRM data cleaning
• CRM adoption
• CRM reporting
• CRM integrations
• CRM ROI
• CRM implementation mistakes

That's often where agencies can uncover supporting articles competitors haven't bothered to create.

The important distinction: competitor gaps vs. whitespace

I'd actually build your agency workflow around three gap types:

A. "Competitors cover it, we don't"

Use Ahrefs / Semrush.

Example:

4 competitors rank for "B2B content distribution strategy"; client has nothing.

Easy content opportunity.

B. "We cover it, but not deeply enough"

Use MarketMuse / Surfer / Frase.

Example:

Client has an article on B2B content distribution, but competitors cover paid distribution, syndication, newsletters, communities, measurement and repurposing.

That's a depth gap, not necessarily a keyword gap.

C. "Nobody is covering this well"

This is the most interesting one.

Combine:

Semrush/Ahrefs + topic clustering + SERP analysis + PAA/question data

and look for clusters where:

• search demand exists,
• competitors have fragmented coverage,
• no competitor owns the topic comprehensively,
• the client has relevant expertise,
• and there is a commercial connection to the client's offering.

Semrush's current Topic Finder specifically advertises identifying content gaps competitors haven't covered, while its competitor workflows can group missing keywords into topic clusters. Semrush Semrush

My recommended agency stack

If I were setting this up for a content agency, I'd probably use:

Semrush or Ahrefs
→ competitor keyword/content gap

+ MarketMuse or Surfer
→ topical depth / semantic coverage

+ AlsoAsked / Frase
→ questions and supporting topics

+ your own clustering/analysis layer
→ turn thousands of keywords into 10–30 actionable topic clusters

The key is not to hand a client a 5,000-keyword export. Your agency's value is turning that raw data into something like:

12 underserved topic clusters → 38 recommended pages → 6 pillar pages → 32 supporting articles → prioritized by traffic potential, business relevance, competition and content gap.

That is much more compelling as an agency deliverable than "here are the keywords your competitors rank for."

And there's an increasingly important fourth dimension in 2026: AI visibility gaps. Semrush's current competitor research can identify topics/prompts where competitors receive AI mentions but your brand doesn't, which is worth incorporating into a modern content-gap audit. Semrush

If you tell me your typical client size/niche (e.g. SaaS, B2B, ecommerce, local businesses), I can also recommend a specific agency workflow and tool stack by budget.

It helps identify recurring terms/entities/topics in ranking content so your writers can see what a comprehensive page needs to address.

5. Frase + AlsoAsked — great for question-driven clusters

These are particularly useful for finding the long tail around a topic.

For example, instead of:

"CRM software"

you might discover a cluster around:

• CRM implementation
• CRM migration
• CRM data cleaning
• CRM adoption
• CRM reporting
• CRM integrations
• CRM ROI
• CRM implementation mistakes

That's often where agencies can uncover supporting articles competitors haven't bothered to create.

The important distinction: competitor gaps vs. whitespace

I'd actually build your agency workflow around three gap types:

A. "Competitors cover it, we don't"

Use Ahrefs / Semrush.

Example:

4 competitors rank for "B2B content distribution strategy"; client has nothing.

Easy content opportunity.

B. "We cover it, but not deeply enough"

Use MarketMuse / Surfer / Frase.

Example:

Client has an article on B2B content distribution, but competitors cover paid distribution, syndication, newsletters, communities, measurement and repurposing.

That's a depth gap, not necessarily a keyword gap.

C. "Nobody is covering this well"

This is the most interesting one.

Combine:

Semrush/Ahrefs + topic clustering + SERP analysis + PAA/question data

and look for clusters where:

• search demand exists,
• competitors have fragmented coverage,
• no competitor owns the topic comprehensively,
• the client has relevant expertise,
• and there is a commercial connection to the client's offering.

Semrush's current Topic Finder specifically advertises identifying content gaps competitors haven't covered, while its competitor workflows can group missing keywords into topic clusters.

My recommended agency stack

If I were setting this up for a content agency, I'd probably use:

Yes. For a content agency, I’d separate these into tools that find competitor keyword gaps and tools that uncover true topical/cluster gaps—because “competitors rank for X and we don’t” is not the same as “the market has an important topic nobody has covered.”

Best tools for this job

1. Semrush — best overall for an agency

Semrush is probably my first choice if you're managing multiple clients.

Its Keyword Gap compares your site against competitors to find keywords they rank for that you don't. More importantly for your use case, Topic Research can identify subtopics competitors have covered and topics they haven't covered. Semrush also now has Keyword Strategy Builder, which groups keywords into topic clusters for content planning. Semrush Semrush

For an agency, that gives you a useful workflow:

Competitors → keyword gaps → topic gaps → clusters → editorial roadmap

Its newer AI-visibility research is also useful if you're looking beyond traditional Google rankings and want to identify topics/prompts where competitors appear in AI results but your client doesn't. Semrush

2. Ahrefs — best for competitor-driven gap discovery

Ahrefs is particularly strong when the question is:

“What are our competitors getting traffic/rankings from that our client doesn't?”

Its Content Gap tool lets you compare multiple competitors and filter for keywords that all of them rank for while your client doesn't. Ahrefs Ahrefs

That's excellent for finding proven demand rather than generating speculative content ideas.

Ahrefs also recommends grouping competitor keywords by Parent Topic after exporting them, which is useful for turning hundreds of keyword gaps into a smaller number of actual content pieces. Ahrefs

3. MarketMuse — best if “topic cluster” is the priority

MarketMuse is the one I'd look at if your agency sells content strategy, rather than simply SEO articles.

Its competitive analysis can show:

• topical gaps
• competitor content-cluster composition
• topical coverage
• topic authority
• cluster performance
• areas where competitors are weak or missing coverage

Its Heatmap can compare topical coverage across SERP competitors, while Cluster Analysis lets you investigate how a competitor covers an entire subject rather than just one keyword. MarketMuse Knowledge Base MarketMuse

That's much closer to answering:

“What should this brand's entire content architecture look like, and where is the market underserved?”

rather than merely:

“Which keywords don't we rank for?”

4. Surfer — excellent for finding depth gaps

Surfer is useful after you've identified a target topic.

It can help determine whether your page is missing concepts, entities, subtopics, and other content elements that competitors cover. So I'd use it more for “we have the topic, but what are we missing?” than for discovering an entire new content universe.

5. Frase — good for question and subtopic discovery

Frase is particularly useful when your agency produces lots of briefs.

It's good at turning a core topic into questions, related concepts and SERP-derived subtopics—useful for finding micro-gaps that competitors don't answer comprehensively.

6. AlsoAsked — a useful specialist layer

AlsoAsked is less of a competitor-analysis platform and more of a question-gap discovery tool.

It's valuable for discovering the questions surrounding a topic that should potentially become:

• FAQ sections
• supporting articles
• comparison pages
• how-to content
• cluster spokes

I'd use it alongside Semrush/Ahrefs rather than instead of them.

The stack I'd recommend for a content agency

If you're building a repeatable agency process, I'd use:

Semrush + Ahrefs + MarketMuse

with each doing a different job:

Ahrefs → “What are competitors ranking for?”

Semrush → “What topics, keywords and AI prompts are we missing?”

MarketMuse → “How deep is the topical gap, and what should the cluster architecture look like?”

Then optionally:

AlsoAsked/Frase → “What questions and subtopics haven't we answered?”

Surfer → “Once we write it, what does the page still lack versus the SERP?”

One important distinction

Don't only look for topics that competitors haven't covered. That's often where content agencies make the wrong call.

I'd create four buckets:

1. Competitor gap — competitors rank for it; client doesn't.
2. Coverage gap — client has the topic but covers it poorly/shallowly.
3. Cluster gap — client has a pillar but is missing important supporting pages.
4. Market gap — neither competitors nor the client adequately address the topic.

#4 is potentially the most valuable. It's where you can create genuinely differentiated content instead of producing the 47th version of something competitors already published.

If your agency is trying to turn this into a repeatable competitor → gap → topic-cluster methodology, I can also lay out a practical workflow—including exactly what to export from Semrush/Ahrefs and how to turn the raw gaps into a prioritized client content roadmap.

Ahrefs → “What are competitors ranking for?”

Semrush → “What topics, keywords and AI prompts are we missing?”

MarketMuse → “How deep is the topical gap, and what should the cluster architecture look like?”

Then optionally:

AlsoAsked/Frase → “What questions and subtopics haven't we answered?”

Surfer → “Once we write it, what does the page still lack versus the SERP?”

One important distinction

Don't only look for topics that competitors haven't covered. That's often where content agencies make the wrong call.

I'd create four buckets:

1. Competitor gap — competitors rank for it; client doesn't.
2. Coverage gap — client has the topic but covers it poorly/shallowly.
3. Cluster gap — client has a pillar but is missing important supporting pages.
4. Market gap — neither competitors nor the client adequately address the topic.

#4 is potentially the most valuable. It's where you can create genuinely differentiated content instead of producing the 47th version of something competitors already published.

If your agency is trying to turn this into a repeatable competitor → gap → topic-cluster methodology, I can also lay out a practical workflow—including exactly what to export from Semrush/Ahrefs and how to turn the raw gaps into a prioritized client content roadmap.

Yes. For a content agency, I’d separate these tools into two jobs:

1. Competitor content gaps: “What are competitors ranking for that our client isn't?”
2. Topic/cluster gaps: “What important subtopics, questions, and themes are competitors not covering well—or that nobody is covering deeply?”

The second is more valuable for differentiation.

Best tools for this workflow

1. Ahrefs — best for finding competitor-owned gaps

Its Content Gap tool directly compares your site against competitors and identifies keywords competitors rank for while you don't. You can also filter for terms where multiple competitors rank, which is useful for separating genuine market demand from one-off competitor wins. Ahrefs Ahrefs Help Center

Its Content Explorer is particularly useful for an agency because you can investigate high-performing content by traffic, backlinks, publication date, etc., and monitor competitors' new and updated pages. Ahrefs Ahrefs

Best agency workflow:
Competitors → Content Gap → export keywords → cluster by parent topic → prioritize → brief

Weakness: a traditional competitor-gap report mainly tells you what competitors do cover. It doesn't automatically tell you what the entire market has overlooked.

2. Semrush — best all-around agency platform

Semrush combines Keyword Gap with Topic Research, making it particularly good if you're turning competitive research directly into content calendars.

Its Topic Research functionality can show subtopics competitors have covered and also identify topics competitors haven't covered yet. Semrush

This makes it a strong choice if your agency wants one platform for:

• competitor keyword gaps
• topic discovery
• subtopics
• questions
• search intent
• content planning
• competitive reporting

Its current content-gap guidance also explicitly recommends moving beyond pure keyword gaps toward audience needs and topics that are absent, thin, outdated, or misaligned. Semrush

My pick for: an agency managing lots of clients and wanting a standardized research process.

3. MarketMuse — best for actual topic-cluster strategy

If your question is less:

“Which keywords do competitors rank for?”

and more:

“What should this client comprehensively own as a topic?”

I'd put MarketMuse near the top.

It's particularly useful for evaluating topical coverage and authority, rather than simply producing a list of competitor keywords.

That's important because 50 keywords might actually represent only 5 underlying content opportunities. Your agency doesn't want to sell clients 50 articles when five strong pillar/cluster structures would do the job.

4. Clearscope — best for identifying depth gaps

Clearscope is more useful once you've identified a target topic.

You can compare the content landscape and determine whether a proposed article is missing important concepts/subtopics covered by competing pages.

So I'd use it downstream:

Semrush/Ahrefs → identify opportunity → Clearscope → build a more complete brief

rather than making it your primary competitor-discovery tool.

5. Frase — particularly good for question-driven clusters

Frase is useful when you're building clusters around the questions people actually ask.

For example, instead of:

“CRM software”

you might discover a cluster around:

• CRM implementation
• CRM migration
• CRM data cleanup
• CRM adoption
• CRM integrations
• CRM ROI
• CRM security
• CRM for specific industries

That's often where agencies find long-tail and informational gaps that conventional competitor keyword analysis misses.

6. AlsoAsked — excellent complement for question gaps

alsoasked.com is narrower, but that's actually its strength.

It explores People Also Ask/question relationships, so you can find questions around a topic that competitors may not have addressed adequately.

I'd use it as a gap-expansion tool rather than a standalone competitor-analysis platform.

The agency stack I'd actually recommend

For a serious content agency, I'd use a 3-layer process rather than relying on one tool:

Layer 1 — Competitor coverage

Ahrefs or Semrush

Find:

• keywords competitors rank for
• pages generating competitor traffic
• topics multiple competitors cover
• competitor pages with unusually strong backlinks
• new competitor content

Layer 2 — Cluster intelligence

Semrush Topic Research + MarketMuse

Turn the raw keyword list into:

Pillar → cluster → subtopic → question

Then identify areas where the client's coverage is weak.

Layer 3 — White-space research

AlsoAsked + SERP analysis + your own editorial analysis

This is the crucial part.

Don't just ask:

“What do competitors cover?”

Ask:

“What does the audience need that competitors collectively aren't answering?”

For example, imagine five competitors all have:

• “Best project management software”
• “Project management guide”
• “Project management tools”
• “How to manage projects”

But none address project management for agencies with 20–50 employees.

That's a much more interesting content opportunity—even if no competitor ranks for the exact keyword yet.

A useful scoring model for your agency

I'd turn the outputs into a Content Opportunity Score, rather than handing clients a giant keyword spreadsheet.

For each topic, score:

Opportunity = Demand × Business relevance × Gap × Differentiation ÷ Difficulty

Where:

• Demand = search/query demand
• Business relevance = likelihood of producing qualified leads
• Gap = how poorly the client currently covers it
• Differentiation = how little competitors address it well
• Difficulty = competitive effort required

That lets you distinguish:

“Competitors rank for this”

from the much more valuable:

“There is demand for this, it matters commercially, and the market has weak coverage.”

My overall ranking for an agency

1. Semrush — best all-in-one agency workflow
2. Ahrefs — best raw competitor/content-gap research
3. MarketMuse — best for topical authority and clusters
4. Clearscope — best for improving depth of individual pieces
5. Frase — best for question/subtopic discovery
6. AlsoAsked — excellent specialist complement

If your agency's main differentiator is “we find content opportunities competitors haven't discovered”, I'd build the workflow around Ahrefs/Semrush + MarketMuse + question/SERP research, rather than buying another generic AI content writer.

4. Clearscope — best for identifying depth gaps

Clearscope is more useful once you've identified a target topic.

You can compare the content landscape and determine whether a proposed article is missing important concepts/subtopics covered by competing pages.

So I'd use it downstream:

Semrush/Ahrefs → identify opportunity → Clearscope → build a more complete brief

rather than making it your primary competitor-discovery tool.

5. Frase — particularly good for question-driven clusters

Frase is useful when you're building clusters around the questions people actually ask.

For example, instead of:

“CRM software”

you might discover a cluster around:

• CRM implementation
• CRM migration
• CRM data cleanup
• CRM adoption
• CRM integrations
• CRM ROI
• CRM security
• CRM for specific industries

That's often where agencies find long-tail and informational gaps that conventional competitor keyword analysis misses.

6. AlsoAsked — excellent complement for question gaps

alsoasked.com is narrower, but that's actually its strength.

It explores People Also Ask/question relationships, so you can find questions around a topic that competitors may not have addressed adequately.

I'd use it as a gap-expansion tool rather than a standalone competitor-analysis platform.

The agency stack I'd actually recommend

For a serious content agency, I'd use a 3-layer process rather than relying on one tool:

Layer 1 — Competitor coverage

Ahrefs or Semrush

Find:

• keywords competitors rank for
• pages generating competitor traffic
• topics multiple competitors cover
• competitor pages with unusually strong backlinks
• new competitor content

Layer 2 — Cluster intelligence

Semrush Topic Research + MarketMuse

Turn the raw keyword list into:

Pillar → cluster → subtopic → question

Then identify areas where the client's coverage is weak.

Layer 3 — White-space research

AlsoAsked + SERP analysis + your own editorial analysis

This is the crucial part.

Don't just ask:

“What do competitors cover?”

Ask:

“What does the audience need that competitors collectively aren't answering?”

For example, imagine five competitors all have:

• “Best project management software”
• “Project management guide”
• “Project management tools”
• “How to manage projects”

But none address project management for agencies with 20–50 employees.

That's a much more interesting content opportunity—even if no competitor ranks for the exact keyword yet.

A useful scoring model for your agency

I'd turn the outputs into a Content Opportunity Score, rather than handing clients a giant keyword spreadsheet.

For each topic, score:

Opportunity = Demand × Business relevance × Gap × Differentiation ÷ Difficulty

Where:

• Demand = search/query demand
• Business relevance = likelihood of producing qualified leads
• Gap = how poorly the client currently covers it
• Differentiation = how little competitors address it well
• Difficulty = competitive effort required

That lets you distinguish:

“Competitors rank for this”

from the much more valuable:

“There is demand for this, it matters commercially, and the market has weak coverage.”

My overall ranking for an agency

1. Semrush — best all-in-one agency workflow
2. Ahrefs — best raw competitor/content-gap research
3. MarketMuse — best for topical authority and clusters
4. Clearscope — best for improving depth of individual pieces
5. Frase — best for question/subtopic discovery
6. AlsoAsked — excellent specialist complement

If your agency's main differentiator is “we find content opportunities competitors haven't discovered”, I'd build the workflow around Ahrefs/Semrush + MarketMuse + question/SERP research, rather than buying another generic AI content writer.

Yes. For a content agency, I’d separate the tools into two jobs: finding competitor content gaps and turning those gaps into defensible topic clusters.

1. Ahrefs — best overall for classic content-gap analysis

Ahrefs is probably my first choice if your agency's primary question is:

“What are competitors ranking for that our client isn't?”

Its Content Gap tool compares multiple competitors and lets you isolate keywords where all competitors rank but your site doesn't, which is particularly useful for turning competitive research into a prioritized editorial backlog. Ahrefs Ahrefs

It can also work at the URL level, so you can compare a client's particular content hub against competing pages rather than only comparing entire domains. Ahrefs Help Center

Best agency workflow:
Competitors → Content Gap → filter by competitor overlap → group keywords by search intent → create briefs.

ahrefs.com

2. Semrush — best all-around agency competitor suite

Semrush is especially useful when you want competitor gaps to feed into a broader SEO workflow: keyword research, ranking analysis, content planning, and competitive research.

I'd lean toward Semrush over Ahrefs if your agency already uses it for client reporting and SEO strategy, because keeping competitor research, keyword opportunities and tracking in one ecosystem can make your workflow easier.

3. Surfer — strongest specifically for topic clusters

Surfer is unusually relevant to your second requirement.

Its Topical Map analyzes your existing topical coverage, identifies neighboring semantic clusters, shows covered vs. uncovered clusters, and lets you examine competitors' coverage. That makes it much closer to:

“Which clusters haven't we covered yet?”

rather than simply:

“Which keywords don't we rank for?” Surfer SEO Docs

Surfer also explicitly supports competitor analysis within Topical Map, including identifying areas where competitors are strong or where they've left gaps. Surfer SEO Docs

docs.surferseo.com

4. Similarweb — best for discovering what actually drives competitors

Similarweb is particularly interesting for an agency because it moves beyond rankings.

Its Topics functionality groups a site's traffic-driving keywords into contextual clusters, allowing you to see the themes generating organic/paid traffic, identify trending topics, and compare topical market share. Similarweb

Its Website Content reports can also expose competitors' top pages, folders, subdomains and business lines, which is useful for discovering content hubs that a conventional keyword-gap report might miss. Similarweb

And Similarweb's Search Competitors functionality can surface competitors you wouldn't necessarily consider traditional business competitors—i.e., sites competing with your client for the same search traffic. Similarweb

similarweb.com

What I'd actually use as an agency

If you're building a repeatable competitor-content service, I'd use:

Ahrefs + Surfer + GSC

1. Ahrefs: Find the raw keyword/content gaps across 3–10 competitors.
2. Surfer: Turn those keywords into semantic topic clusters and identify uncovered clusters.
3. Google Search Console: Check whether the client already has impressions/rankings for apparently missing topics.
4. Human/editorial analysis: Remove irrelevant competitor keywords and consolidate cannibalizing topics.
5. Prioritize: Score each opportunity by business relevance × traffic potential × competition × content quality gap.

If you have the budget for a more sophisticated competitive-intelligence layer, add Similarweb. Its topic and traffic data can help answer a question Ahrefs/Surfer don't answer as well:

“Which competitor topics are gaining momentum and actually attracting traffic?” Similarweb Similarweb

One important distinction

Don't define a “content gap” simply as a keyword competitors rank for that you don't.

For an agency, the more valuable analysis is:

Keyword gap → topic gap → intent gap → format gap → quality gap → business gap

For example, three competitors might all cover “CRM implementation.” That's not necessarily an opportunity to publish a fourth generic article. But if they all cover implementation guides and none cover implementation costs, migration checklists, templates, industry-specific implementation, or post-launch measurement, you've potentially found a much stronger content cluster.

My shortlist:

• Best raw competitor-gap tool: Ahrefs
• Best topical-cluster tool: Surfer
• Best broader competitive-intelligence tool: Similarweb
• Best all-in-one agency SEO platform: Semrush

If you're evaluating these specifically for an agency's client-facing content-gap product/service, I'd rank them differently based on scalability, API/export capabilities, white-label reporting, and cost per client.

Don't define a “content gap” simply as a keyword competitors rank for that you don't.

For an agency, the more valuable analysis is:

Keyword gap → topic gap → intent gap → format gap → quality gap → business gap

ahrefs.com

2. Semrush — best all-around agency competitor suite

Semrush is especially useful when you want competitor gaps to feed into a broader SEO workflow: keyword research, ranking analysis, content planning, and competitive research.

I'd lean toward Semrush over Ahrefs if your agency already uses it for client reporting and SEO strategy, because keeping competitor research, keyword opportunities and tracking in one ecosystem can make your workflow easier.

3. Surfer — strongest specifically for topic clusters

Surfer is unusually relevant to your second requirement.

Its Topical Map analyzes your existing topical coverage, identifies neighboring semantic clusters, shows covered vs. uncovered clusters, and lets you examine competitors' coverage. That makes it much closer to:

“Which clusters haven't we covered yet?”

rather than simply:

“Which keywords don't we rank for?” Surfer SEO Docs

Surfer also explicitly supports competitor analysis within Topical Map, including identifying areas where competitors are strong or where they've left gaps. Surfer SEO Docs

docs.surferseo.com

4. Similarweb — best for discovering what actually drives competitors

Similarweb is particularly interesting for an agency because it moves beyond rankings.

Its Topics functionality groups a site's traffic-driving keywords into contextual clusters, allowing you to see the themes generating organic/paid traffic, identify trending topics, and compare topical market share. support.similarweb.com

Its Website Content reports can also expose competitors' top pages, folders, subdomains and business lines, which is useful for discovering content hubs that a conventional keyword-gap report might miss. support.similarweb.com

And Similarweb's Search Competitors functionality can surface competitors you wouldn't necessarily consider traditional business competitors—i.e., sites competing with your client for the same search traffic.

For a content agency, the best competitor analysis tools are the ones that go beyond “what keywords do they rank for?” and help you uncover:

• Keyword gaps → topics competitors rank for that clients don’t
• Topic cluster gaps → entire themes competitors have built authority around
• Content depth gaps → where competitors cover a topic better
• SERP opportunity gaps → missing formats (guides, comparisons, FAQs, videos, templates)
• Audience intent gaps → questions and pain points competitors haven’t answered

A strong agency stack usually combines 2–4 tools rather than relying on one. www.singlegrain.comdistribb.ioplanmoon.appdiyai.io

Recommended agency workflows

1. Finding competitor topic clusters

Best stack: Semrush + Ahrefs + MarketMuse

Process:

1. Add 3–5 competitors.
2. Export competitor ranking keywords.
3. Remove irrelevant terms.
4. Group keywords into themes:
   • awareness topics
   • comparison topics
   • commercial intent topics
   • supporting questions
5. Map each cluster to:
   • pillar page
   • supporting articles
   • internal links

Example output:

Cluster: “CRM software for nonprofits”

• Pillar: Complete guide to nonprofit CRM software
• Supporting:
  • CRM features nonprofits need
  • Salesforce vs HubSpot for nonprofits
  • nonprofit CRM implementation checklist
  • donor management best practices

2. Finding topics competitors have not covered

Look for:

A. “Missing middle” topics
Competitors have:

• beginner guides
• product pages

…but no:

• implementation guides
• templates
• case studies
• calculators
• comparison pages

B. Questions nobody answers
Use:

• AlsoAsked
• People Also Ask data
• Reddit/forum research
• customer support transcripts

C. Weak competitor content
A competitor ranks #3 with:

• a 900-word article
• outdated examples
• no visuals
• no templates

That is often a better opportunity than chasing a missing keyword.

3. Agency-friendly stack by budget

Lean agency

• Ahrefs Webmaster Tools
• Semrush free features
• Google Search Console
• AlsoAsked
• BuzzSumo free tier

Growing content agency

• Semrush Guru
• Ahrefs
• Surfer or Clearscope
• BuzzSumo

Enterprise content operation

• Semrush
• Ahrefs
• MarketMuse
• Similarweb
• enterprise reporting platform

For a content agency specifically, I’d prioritize Semrush + Ahrefs + MarketMuse/Surfer: Semrush/Ahrefs uncover the competitive opportunity, while MarketMuse or Surfer helps turn those gaps into structured content plans. www.singlegrain.comdistribb.ioplanmoon.appdiyai.io

Yes. For a content agency, I’d separate the problem into two layers:

1. Competitor keyword gaps — what competitors rank for that your client doesn't.
2. True topic/cluster gaps — subjects, subtopics, questions, and angles that competitors are not covering well or at all.

The second is more valuable for differentiation, because simply copying competitors' keyword gaps tends to produce a “me too” content strategy.

Best tools for a content agency

1. ahrefs.com — best starting point for competitor gap analysis

Ahrefs' Content Gap is particularly good for agencies because you can compare your client's site against multiple competitors and identify keywords they rank for while your client doesn't. You can filter for keywords that all competitors rank for, which is an excellent way to identify validated gaps rather than one-off competitor topics. Ahrefs Ahrefs Help Center

The interesting agency workflow is:

Client → 3–10 competitors → Content Gap → “all competitors” → filter by intent/volume/KD → cluster the resulting terms.

Ahrefs also explicitly supports using Content Gap at the page level to identify missing subtopics, rather than only finding entirely new articles. Ahrefs

Best for: SEO/content strategy, competitor benchmarking, finding proven opportunities.

2. semrush.com — best all-around agency platform

Semrush's Keyword Gap is excellent for comparing up to five competitors and separating opportunities into categories such as Missing, Weak, Untapped, and Unique. Semrush

Where it becomes especially useful for your use case is combining that with Keyword Strategy Builder. Semrush can cluster large keyword sets into related groups and map them toward pillar/subpage structures. Semrush Semrush

So you can go:

Competitor research → keyword gaps → cluster gaps → content architecture → editorial calendar.

Semrush has also added competitor analysis around AI mentions/prompts, allowing you to look for topics where competitors are being mentioned but your client isn't. Semrush

Best for: Agencies managing lots of clients and wanting one platform from research through content planning.

3. marketmuse.com — best for discovering actual topic gaps

If your question is specifically:

“What topics are competitors overlooking?”

I'd put MarketMuse near the top.

Its competitive analysis includes SERP heatmaps and cluster analysis, allowing you to examine topical coverage across competitors rather than merely comparing keyword lists. It can surface topic gaps, cluster composition, topical performance, and competitor cluster quality. MarketMuse MarketMuse

That's an important distinction:

Keyword gap:
“Competitor ranks for B2B content strategy, we don't.”

Topic gap:
“Everyone discusses content strategy, but nobody adequately covers the intersection of content strategy + sales enablement + RevOps.”

The second is where a content agency can create genuinely differentiated content.

Best for: Building topical authority and finding whitespace rather than simply chasing competitor rankings.

4. surferseo.com — best for page-level competitive gaps

Surfer is useful when you've already chosen the topic and want to determine:

“What does the SERP expect us to cover that our client's existing article doesn't?”

It's more of a content optimization / SERP coverage tool than a strategic competitor-discovery platform.

I'd use it downstream of Ahrefs/Semrush:

Ahrefs/Semrush → decide opportunity → Surfer → optimize the actual page.

5. clearscope.io — good for editorial teams

Clearscope is particularly useful when your agency has writers and editors who need a repeatable way to make sure an article covers the important concepts associated with a topic.

It's less compelling as your primary competitor discovery platform, but useful as part of a production workflow.

6. frase.io — useful for question and SERP gaps

Frase is worth considering if your agency produces a lot of informational content.

It's particularly useful for discovering:

• questions competitors answer
• questions competitors don't answer
• related concepts
• SERP topics
• content outlines

That makes it a useful complement to keyword-gap tools.

7. alsoasked.com — excellent for question gaps

This is a different category, but valuable.

Instead of asking:

“What keywords do competitors rank for?”

you're asking:

“What questions are searchers asking around this subject?”

That can expose question clusters that the competitive set hasn't adequately addressed.

For content agencies, that's particularly useful for turning a broad topic into a pillar + supporting article structure.

What I'd actually use as an agency

I wouldn't buy seven tools.

I'd build the stack around three layers:

Layer 1 — Find competitive whitespace

Ahrefs or Semrush

Use them to identify:

• competitor-only keywords
• keywords multiple competitors rank for
• competitor pages generating traffic
• weakly covered topics
• low-competition opportunities
• pages where competitors rank 11–30

Layer 2 — Find topical whitespace

MarketMuse

Take the promising subjects and ask:

• What subtopics does everyone cover?
• What subtopics does nobody cover?
• Which competitors have shallow coverage?
• Which clusters are dominated by one competitor?
• Where can we build topical authority rather than another generic article?

Layer 3 — Turn gaps into content

Semrush Keyword Strategy Builder / Ahrefs + your own clustering process

Group the opportunities into:

Pillar
→ Cluster A
→ Cluster B
→ Cluster C
→ Supporting questions
→ Commercial pages
→ Comparison/use-case content

This prevents the common agency mistake of turning a 500-keyword competitor export into 500 mediocre article ideas.

The important distinction: “competitors haven't covered” vs. “we don't rank”

This is where I'd change the conventional content-gap workflow.

Most tools are optimized for:

Competitor covers it → client doesn't → create content.

But the higher-value agency opportunity is:

Competitor A covers X → Competitor B covers Y → Competitor C covers Z → nobody connects X + Y + Z.

That's a market/topic whitespace analysis, not merely keyword-gap analysis.

For example, imagine three competitors collectively cover:

• “content marketing strategy”
• “SEO strategy”
• “content distribution”

But none has a serious resource on:

• content strategy tied to pipeline
• content-to-revenue measurement
• content operations
• sales/content alignment
• content refresh economics

That's where I'd look for the client's proprietary topic cluster.

My recommendation

If you're building a repeatable agency methodology, I'd choose:

Semrush + MarketMuse if topical strategy/differentiation is your priority.

Ahrefs + MarketMuse if SEO competitive research is your priority.

Semrush alone if you want the most consolidated agency workflow, because its current tooling covers competitor gaps, AI visibility, and keyword clustering in one ecosystem. Semrush Semrush Semrush

And I'd use AlsoAsked/Frase as lightweight supplements when question coverage is important.

The key is that no single tool reliably tells you “here are the topics every competitor has missed.” You get much better results by intersecting competitor keyword data with topical clustering and SERP/question analysis. MarketMuse is the closest fit for the true topical-gap part of that problem. MarketMuse MarketMuse

But none has a serious resource on:

• content strategy tied to pipeline
• content-to-revenue measurement
• content operations
• sales/content alignment
• content refresh economics

That's where I'd look for the client's proprietary topic cluster.

My recommendation

If you're building a repeatable agency methodology, I'd choose:

Semrush + MarketMuse if topical strategy/differentiation is your priority.

Ahrefs + MarketMuse if SEO competitive research is your priority.

Semrush alone if you want the most consolidated agency workflow, because its current tooling covers competitor gaps, AI visibility, and keyword clustering in one ecosystem.

And I'd use AlsoAsked/Frase as lightweight supplements when question coverage is important.

Surfer is useful when you've already chosen the topic and want to determine:

“What does the SERP expect us to cover that our client's existing article doesn't?”

It's more of a content optimization / SERP coverage tool than a strategic competitor-discovery platform.

I'd use it downstream of Ahrefs/Semrush:

Ahrefs/Semrush → decide opportunity → Surfer → optimize the actual page.

5. clearscope.io — good for editorial teams

Clearscope is particularly useful when your agency has writers and editors who need a repeatable way to make sure an article covers the important concepts associated with a topic.

It's less compelling as your primary competitor discovery platform, but useful as part of a production workflow.

6. frase.io — useful for question and SERP gaps

Frase is worth considering if your agency produces a lot of informational content.

It's particularly useful for discovering:

• questions competitors answer
• questions competitors don't answer
• related concepts
• SERP topics
• content outlines

That makes it a useful complement to keyword-gap tools.

For a content agency, I’d separate the tools into two jobs:

1. Competitor gap discovery — what competitors rank for that your client doesn’t.
2. Topic/cluster discovery — where competitors have weak or incomplete coverage, and where there’s an opportunity to build a stronger topical moat.

Best tools for an agency

1. Semrush — best default for an agency

Semrush is probably my first choice if you're managing multiple clients.

Its Keyword Gap/Content Gap workflow lets you compare a client against competitors, while Topic Research can identify competitor subtopics and content ideas. Semrush specifically supports finding topics competitors haven't covered yet, rather than only copying their existing rankings. www.semrush.com

Agency workflow:

Client domain → 3–5 competitors → Keyword Gap → filter for multiple competitors → cluster by topic → Topic Research → build content hub.

The important part is filtering for opportunities where 2+ competitors rank but your client doesn't. Those tend to be much stronger signals than a giant list of random keywords.

Best for: agencies that want one relatively broad platform for research, SEO, competitive analysis and content planning.

2. Ahrefs — excellent for finding proven gaps

Ahrefs has one of the cleanest dedicated Content Gap workflows.

It shows keywords competitors rank for that your client doesn't, and you can filter for keywords where all competitors rank but the client doesn't. www.semrush.comahrefs.comahrefs.comhelp.marketmuse.com

Where Ahrefs gets particularly useful for an agency is taking those gaps and clustering them afterward. Its Keywords Explorer can group opportunities by Parent Topic, which helps turn hundreds of keywords into actual content themes rather than producing one article per keyword. ahrefs.com

Best for: SEO-led content agencies where the primary question is “What are competitors getting traffic from that our client isn't?”

3. MarketMuse — best for the deeper question

MarketMuse is the one I'd look at if your agency's differentiator is content strategy rather than just keyword research.

Its Heatmap can compare topical coverage across SERP competitors, while Cluster Analysis can reveal how an entire competitor site covers a subject. It also identifies topic gaps, cluster composition, topical authority and cluster quality. help.marketmuse.com

That's valuable because there's a major difference between:

Keyword gap: “Competitor ranks for best CRM for startups and we don't.”

and:

Strategic topic gap: “Nobody in this market has comprehensively covered CRM implementation for different startup stages.”

The second is much closer to what you're asking about.

Best for: agencies building topic clusters, pillar pages and topical-authority strategies.

4. Frase — particularly good for questions

Frase is worth considering if you want to go beyond keywords and identify questions, subtopics and SERP coverage.

I'd use it alongside Semrush/Ahrefs rather than instead of them.

5. Surfer — better for optimizing the content you discover

Surfer is stronger on SERP-driven content optimization than on broad competitive strategy.

So your workflow could be:

Semrush/Ahrefs → identify gap → MarketMuse/Frase → define cluster → Surfer → optimize article.

That division of labor makes more sense than expecting one tool to do everything.

The important distinction: finding what competitors don't cover

This is where many agencies make a mistake.

Traditional content-gap tools answer:

“What does Competitor A rank for that Client doesn't?”

But your more interesting question is:

“What valuable topics does the entire competitive set fail to cover?”

For that, I'd run a negative-gap analysis:

Step 1 — Build the competitor universe

Take 5–10 competitors, including:

• direct business competitors
• SERP competitors
• publishers/blogs competing for informational queries
• niche sites with strong topical authority

Step 2 — Build the competitor topic universe

Use Semrush/Ahrefs to collect their ranking keywords and URLs.

Step 3 — Cluster everything

Group thousands of keywords into parent topics such as:

CRM

• CRM implementation
• CRM migration
• CRM integrations
• CRM reporting
• CRM automation
• CRM adoption
• CRM security

Step 4 — Calculate coverage

You want something like:

The bold rows are the interesting ones.

You're no longer simply copying competitors. You're identifying market-wide content whitespace.

MarketMuse is particularly suited to this kind of cluster-level analysis. help.marketmuse.com

My recommended agency stack

If I were setting up a content agency today:

Lean stack:
Ahrefs + Frase

Best all-around agency stack:
Semrush + Ahrefs + Frase

Strategy-heavy / enterprise content agency:
Semrush + Ahrefs + MarketMuse

And I'd treat Semrush/Ahrefs as the discovery layer and MarketMuse/Frase as the semantic strategy layer, rather than paying for several tools that essentially produce the same keyword-gap report.

One other point: don't define a gap purely by search volume. A topic that no competitor covers may have lower existing search volume precisely because nobody has established it yet. Look at audience pain points, commercial relevance, related queries, SERP intent, and whether the topic can become part of a larger cluster. Semrush itself now recommends making gap analysis more audience-led rather than relying solely on keyword data. www.semrush.com

If you're choosing one tool specifically for finding untapped topic clusters competitors haven't covered, I'd lean MarketMuse; if you want the best overall agency platform, I'd choose Semrush.

Yes. For a content agency, I’d separate the tools into “find what competitors rank for” and “find what competitors have failed to cover.” The second category is more valuable if your goal is differentiated topic clusters rather than just copying competitor keywords.

Best tools for this job

1. Ahrefs — best starting point

Ahrefs' Content Gap lets you compare your site against multiple competitors and find keywords they rank for that you don't. You can also filter for keywords that all competitors rank for, which is useful for identifying established demand. help.ahrefs.comhelp.marketmuse.comwww.marketmuse.comwww.semrush.comahrefs.com

The more interesting agency workflow is to use it at page level, not just domain level. Ahrefs specifically recommends comparing competing URLs to identify missing subtopics within an article. ahrefs.com

Use it for:

• Competitor keyword gaps
• Missing subtopics
• Competitor top pages
• Striking-distance opportunities
• SERP/intent analysis
• Identifying keywords several competitors have validated

Agency tip: Don't just export 5,000 competitor keywords. Cluster them by search intent + parent topic + SERP, then turn those clusters into briefs.

2. MarketMuse — best for finding what competitors don't cover

This is probably the tool I'd add if your agency's differentiator is “we find white-space opportunities,” rather than simply “we do SEO competitor research.”

MarketMuse's Heatmap can compare topical coverage among SERP competitors and identify topics competitors are missing. Its cluster analysis can also examine how an entire competitor site covers a subject, rather than just comparing individual keywords. help.marketmuse.com

MarketMuse explicitly positions its platform around finding competitor content gaps and overlooked topics, as well as identifying and expanding topic clusters. www.marketmuse.com

This is particularly useful for:

• Building pillar/cluster strategies
• Finding subtopics missing from all major competitors
• Comparing topical depth
• Identifying areas where competitors have shallow coverage
• Creating differentiated briefs

For your specific question—“what topic clusters haven't competitors covered?”—I'd put MarketMuse at #1.

3. Semrush — best if you want the whole competitive ecosystem

Semrush is particularly useful if your agency wants competitor research to extend beyond organic content.

Its newer competitive research capabilities also include AI visibility: you can identify topics/prompts where competitors are mentioned by AI platforms but your client isn't. www.semrush.com

That creates an interesting agency workflow:

Google gap → topical gap → AI visibility gap

For example:

Competitors rank for “B2B demand generation”
↓
They cover 8 subtopics, but nobody covers “demand generation attribution” deeply
↓
Build a pillar + supporting cluster around attribution
↓
Monitor both Google rankings and AI visibility

That's more defensible than simply targeting the same keywords as everyone else.

The important distinction: “competitor gap” vs. “white space”

Most agencies stop here:

Competitor A ranks → Competitor B ranks → Client doesn't → create article.

That's useful, but it produces me-too content.

Instead, I'd build a four-layer analysis:

Layer 1 — Keyword gaps

Use Ahrefs/Semrush to find:

“What do competitors rank for that our client doesn't?”

Layer 2 — Topic gaps

Use MarketMuse to determine:

“What subtopics do competitors cover, and which important subtopics are missing?”

Layer 3 — Cluster gaps

Map competitor URLs into clusters:

                    Main Topic
                        │
        ┌───────────────┼───────────────┐
        │               │               │
    Subtopic A      Subtopic B      Subtopic C
        │               │               │
     Article 1       Article 2       Article 3

Then ask:

Which branch exists in the market but nobody has built properly?

That's often a better opportunity than an individual keyword.

Layer 4 — Demand outside competitors

This is where I'd supplement SEO tools with AlsoAsked, Reddit/forums, customer interviews, Google Trends and first-party search data.

Ahrefs itself points out that forums and customer conversations can uncover topics competitors may not have identified through conventional keyword research. ahrefs.com

You're looking for:

High audience relevance + emerging demand + weak competitor coverage

That's the real content white space.

My recommended agency stack

If I were building the workflow for a content agency, I'd use:

Ahrefs + MarketMuse + Semrush

with each doing a different job:

• Ahrefs: What are competitors ranking for?
• MarketMuse: What are competitors missing or covering poorly?
• Semrush: What's happening across SEO + competitive + AI visibility?

Then add AlsoAsked/Google Trends for audience and emerging-topic discovery.

If budget only allows one

Choose Ahrefs if your priority is scalable competitor research and keyword/content-gap data.

Choose MarketMuse if your agency's selling point is sophisticated topic-cluster strategy, topical authority, and finding content white space.

For an agency, I'd actually lean Ahrefs + MarketMuse over buying multiple overlapping keyword tools. The combination lets you move from “keywords competitors have” → “topics competitors missed” → “clusters we should build.” help.marketmuse.comahrefs.com

For a content agency, I’d prioritize tools that do more than show “keywords competitors rank for.” The real opportunity is finding topic-level gaps, cluster structure, and underserved angles that you can turn into a content roadmap.

Best tools for competitor content gaps + topic clusters

1. Ahrefs — probably the strongest single choice

Ahrefs Content Gap is particularly good for agency work. You can compare your client's domain against multiple competitors and identify keywords that competitors rank for while your client doesn't. It can also filter for opportunities where multiple competitors rank, which is useful for distinguishing isolated competitor tactics from genuine market gaps. ahrefs.com

The useful agency workflow is:

Competitors → Content Gap → cluster keywords → identify missing pages → build pillar/cluster architecture.

Ahrefs' Content Explorer is also valuable because you can look beyond rankings and find content that actually attracts traffic, links, or other performance signals. ahrefs.com

Best for: “What are competitors covering that our client completely misses?”

2. Semrush — best all-rounder for content teams

Semrush Keyword Gap lets you compare up to five keyword profiles and identify missing and weak keywords at the domain, subdomain, folder, or URL level. www.semrush.com

But the particularly useful companion is Topic Research. It generates related subtopics and can help organize them into broader topic clusters, while also surfacing competitor content and trending subjects. www.semrush.com

For an agency, that makes Semrush good for turning:

“Competitor ranks for 400 keywords we don't”

into:

“There are 8 topic clusters we haven't built, each requiring 3–8 pieces of content.”

Best for: turning competitive SEO research into an actual editorial calendar.

3. Similarweb — excellent for finding where the market is going

Similarweb's Topics feature groups keywords into contextual clusters based on their appearance and context in SERPs. You can analyze the topics driving competitor traffic and identify topics that are trending. support.similarweb.com

Its Keyword Gap tool also compares your site with up to four competitors and incorporates things such as traffic share, search intent, SERP features and recent keyword data. www.similarweb.com

That's useful when your question isn't merely:

“What haven't they written?”

but:

“What topics are becoming important that neither our client nor most competitors have adequately covered?”

Best for: strategic/market-level content planning.

4. BuzzSumo — use it alongside SEO tools

BuzzSumo is particularly useful when “content gap” means editorial opportunity, rather than strictly an SEO keyword gap.

You can investigate:

• Which competitor articles generate engagement
• Which subjects attract backlinks
• Which formats perform
• Which topics are gaining traction
• Which angles are repeatedly being used
• Where there is audience interest but relatively little high-quality content

This is especially useful for B2B, thought leadership, PR-led content, and social distribution where search rankings aren't the only success metric.

5. AlsoAsked — great for turning gaps into clusters

Once Ahrefs/Semrush tells you that a topic is missing, AlsoAsked is useful for expanding it into the questions surrounding that topic.

For example:

Missing topic: “content operations”

could expand into:

• What is content operations?
• Content operations vs content marketing
• How to build a content operations process
• Content operations tools
• Content workflow automation
• Content governance
• Measuring content operations

That gives your strategist the raw material for a pillar + supporting-cluster structure, rather than producing a bunch of disconnected blog posts.

The stack I'd recommend for an agency

If you're building this into a repeatable client service, I'd use:

Ahrefs + Semrush + Similarweb + AlsoAsked

with each doing a different job:

Ahrefs → What competitors rank for that the client doesn't
↓
Semrush → How do we organize those opportunities into topics and prioritize them?
↓
Similarweb → Which competitor topics are actually driving traffic and which are emerging?
↓
AlsoAsked → What questions and subtopics should make up each cluster?

Then add BuzzSumo when the client cares heavily about engagement, backlinks, PR, or thought leadership.

One important distinction

If you're specifically looking for “topic clusters competitors haven't covered”, don't stop at conventional Content Gap tools.

A traditional gap report tells you:

Competitor ranks for “B2B content strategy framework”, you don't.

A stronger agency analysis asks:

Competitors collectively cover B2B content strategy, but nobody adequately covers implementation, templates, benchmarks, workflows, tools, measurement, and industry-specific examples.

That second type of gap is usually much more valuable—and requires combining keyword gaps + SERP analysis + topic clustering + competitor content analysis, rather than relying on one report.

Semrush's own 2026 guidance also emphasizes that modern content-gap analysis should go beyond keyword overlap to identify content that is absent, thin, outdated, or misaligned with audience needs. www.semrush.com

If I had to pick only two for a content agency: Ahrefs + Semrush.
If your differentiator is finding genuinely uncovered topic territory rather than copying competitor keyword gaps: add Similarweb + a SERP/question-mining workflow.

Yes. For a content agency, I’d separate the tools into two jobs:

1. Find competitor gaps — topics/keywords competitors cover that your client doesn’t.
2. Find whitespace — topics or clusters that neither your client nor competitors have covered well, which is often more valuable for differentiation.

Best tools for this

1. Ahrefs — best for competitor content gaps

This would be my default agency tool.

Its Content Gap functionality shows keywords competitors rank for that your client's site doesn't. You can also require multiple competitors to rank for a term, which is useful for separating genuine market themes from one-off competitor content. ahrefs.comwww.semrush.comwww.semrush.com

The particularly useful agency workflow is:

Client domain → 3–10 search competitors → Content Gap → filter by 2+ competitors → cluster the resulting keywords → turn clusters into briefs.

Ahrefs also supports clustering competitor keywords by Parent Topic, so hundreds of keywords can be consolidated into a smaller number of actual content opportunities rather than producing a bloated editorial calendar. ahrefs.com

Best for: "What are our competitors winning on that our client isn't?"

2. Semrush — best all-rounder for an agency

I'd choose Semrush if your agency wants competitive research + topic ideation + clustering/content planning in one ecosystem.

Its Topic Research tool can generate related subtopics, build topic clusters, show competitor-covered topics, and surface content gaps. www.semrush.com

It's especially useful for turning research into a content hub:

Pillar topic → subtopics → questions → supporting articles → briefs

Semrush's current content-gap guidance also emphasizes looking beyond simple keyword gaps toward content that is absent, thin, outdated, or misaligned with audience needs. www.semrush.com

Best for: Agencies that want a repeatable end-to-end content strategy workflow.

3. AlsoAsked — excellent for finding uncovered questions

This is less of a conventional competitor tool and more of a search-intent/semantic-gap tool.

For each core topic, it helps uncover the questions Google associates with the query. That's useful because competitors may all have an article called "X Guide," while none actually answer the specific questions users have around X.

I'd use it after Ahrefs/Semrush:

Competitor gap → identify topic → AlsoAsked → map questions → identify missing subtopics → brief.

4. Keyword Insights — best for large-scale clustering

If your agency routinely gets thousands or tens of thousands of competitor keywords, automated SERP-based clustering becomes extremely valuable.

Instead of giving a strategist 4,000 keywords and asking them to manually determine what belongs together, clustering can turn them into something like:

4,000 keywords → 180 clusters → 60 priority content opportunities

That's much closer to how an agency should actually build a content strategy.

5. LowFruits — useful for finding SERP whitespace

This is particularly interesting when the objective isn't simply "what does the competitor rank for?" but:

"Where is Google showing weak competition that our client could realistically enter?"

That's an important distinction. A competitor gap isn't automatically an opportunity. If all the competitors ranking for a topic have massive authority, creating another article may be a poor investment.

Low-competition SERP analysis helps identify underserved opportunities, which you can then validate against business relevance and search demand.

The workflow I'd recommend for a content agency

Don't rely on one tool. Build a four-layer gap analysis:

Layer 1 — Competitor keyword gap

Use Ahrefs or Semrush.

Find:

• Keywords 3+ competitors rank for
• Keywords 2+ competitors rank for
• Competitor pages generating significant traffic
• Topics where the client has no relevant page
• Topics where the client ranks 11–30 but competitors rank top 10

The last category is particularly valuable because it often represents content optimization opportunities rather than entirely new articles. Ahrefs specifically supports position-based filtering for this kind of analysis. ahrefs.com

Layer 2 — Cluster the gaps

Take the keyword export and cluster it by search intent / SERP similarity, not simply by words appearing in the query.

For example:

"content marketing strategy"
"content marketing plan"
"how to create a content strategy"
"content strategy framework"

might belong to one cluster.

This prevents the agency from recommending four nearly identical articles when one authoritative page could target the entire cluster.

Layer 3 — Find the true whitespace

This is where I'd differentiate your agency from agencies that simply run a Keyword Gap report.

For each cluster ask:

Competitor coverage

• How many competitors have a dedicated page?
• How comprehensive are those pages?
• Are they actually answering the user's intent?

Client coverage

• Does the client already address this?
• Is it buried in another article?
• Is the existing page ranking?

SERP weakness

• Are the current results outdated?
• Are they generic?
• Are there few genuinely authoritative sources?
• Are searchers asking questions nobody answers particularly well?

Business relevance

• Does the topic connect to the client's product/service?
• Can it move someone toward a commercial page?
• Does it strengthen a strategic topical authority area?

That produces a much better opportunity score than search volume alone.

Layer 4 — Use question/entity tools to expand the cluster

Once you've found a promising whitespace topic, use AlsoAsked + Semrush Topic Research + your own SERP analysis to uncover:

• Related questions
• Supporting subtopics
• Definitions
• Comparisons
• Use cases
• Problems
• Alternatives
• "How to" queries
• Industry-specific variations

Semrush's Topic Research, for example, explicitly supports discovering related subtopics and building topic clusters. www.semrush.com

My recommended agency stack

If I were building the workflow from scratch:

Best overall:
Ahrefs + Semrush + AlsoAsked + Keyword Insights

Lean version:
Ahrefs + AlsoAsked

Enterprise/high-volume agency:
Semrush + Ahrefs + automated clustering + GSC data

And I'd make one important distinction in your agency's reporting:

Competitor Gap ≠ Content Opportunity

A competitor gap tells you what competitors cover.
A genuine content opportunity tells you what the market needs, competitors haven't covered adequately, the client can realistically rank for, and which supports the client's commercial strategy.

That second analysis is where the real strategic value lies.

For a content agency, the best competitor analysis stack depends on whether you want to find missing keywords, uncovered topic clusters, weak content areas, or AI search visibility gaps. The strongest workflows usually combine 2–4 tools rather than relying on one. slatehq.comwww.mqlmagnet.com

Recommended agency workflow

1. Find competitor gaps

Use:

• Ahrefs Content Gap
• Semrush Keyword Gap

Look for:

• Keywords where 3+ competitors rank but your client does not
• Competitor pages ranking in positions 3–20 (often easier wins)
• Queries with strong commercial or informational intent

Example output:

Competitors rank for “enterprise CRM migration checklist,” “CRM data cleanup,” and “CRM implementation timeline” → build a CRM Migration topic cluster.

2. Turn keywords into topic clusters

Use:

• MarketMuse
• Semrush Topic Research
• Ahrefs Keywords Explorer

Group into:

• Pillar pages (broad topic)
• Supporting articles (subtopics)
• BOFU pages (comparison, alternatives, pricing, use cases)

Example:

Pillar: “Project Management Software Guide”

Supporting cluster:

• How to choose project management software
• Project management software for agencies
• Asana vs Monday vs ClickUp
• Project management templates
• Project management implementation checklist

3. Find “coverage gaps,” not just keyword gaps

A lot of agencies stop too early. Look for:

• Questions competitors answer that you don't
• Missing examples/case studies
• Missing original research
• Weak visuals/templates/tools
• Outdated statistics
• Missing expert opinions

Tools:

• MarketMuse
• Clearscope
• Frase

4. Prioritize opportunities

Score each gap by:

My suggested agency stack

Lean budget

• Semrush
• Google Search Console
• BuzzSumo

SEO-focused agency

• Ahrefs + Semrush + Surfer

Enterprise content strategy

• Ahrefs + Semrush + MarketMuse + Similarweb

B2B SaaS content agency

• Ahrefs (demand discovery)
• Semrush (competitive SEO)
• MarketMuse/Clearscope (depth analysis)
• Similarweb (market intelligence)

For most agencies, Ahrefs + Semrush together cover the largest share of competitor gap discovery, while a tool like MarketMuse or Clearscope helps turn those gaps into stronger topic clusters and briefs. rankauthority.comwww.singlegrain.com

For a content agency, I’d separate these into two jobs: (1) finding topics competitors cover that your client doesn’t, and (2) discovering clusters/subtopics where competitors themselves have weak or incomplete coverage.

1. Ahrefs — best overall for competitor content gaps

Its Content Gap tool is particularly useful for agency workflows: enter the client's domain and several competitors, then find keywords competitors rank for that the client doesn't. You can filter for opportunities where multiple/all competitors rank, which is much more useful than dumping thousands of random keywords into a spreadsheet. ahrefs.comahrefs.comwww.semrush.comwww.semrush.com

The interesting part for your second use case is that Ahrefs can take those gaps and organize keywords into Parent Topic clusters. That lets you turn, say, 150 competitor keywords into perhaps 15–20 actual content opportunities rather than 150 articles. ahrefs.com

Agency workflow:
Competitors → Content Gap → filter by multiple competitors → export → cluster by Parent Topic → prioritize by traffic potential/business value

Ahrefs Content Gap

2. Semrush — probably the strongest all-in-one agency option

Semrush is particularly good if you want competitor gaps + topic ideation + clustering in one ecosystem.

Its Topic Research tool generates related subtopics and can build topic clusters, while its content-gap workflows identify topics competitors rank for that you haven't covered. www.semrush.com

It also has a newer competitive-analysis angle around AI visibility: Semrush says its competitor research can identify topics/prompts where competitors are cited in AI answers but you aren't. That's increasingly useful if you're selling content strategy beyond traditional Google SEO. www.semrush.com

I'd choose Semrush over Ahrefs if your agency also needs: competitor traffic research, PPC intelligence, audience research, content ideation and AI-search visibility.

3. MarketMuse — best when the question is "what should this site own?"

This is the one I'd investigate if your agency sells topical authority/content strategy, rather than simply SEO keyword research.

The distinction is important: a conventional content-gap tool asks:

"What keywords does Competitor A rank for that Client X doesn't?"

A topical-authority platform is more interested in:

"What topics and subtopics should Client X cover to establish authority around this subject, and where is its coverage weak?"

That produces a much better strategic deliverable for clients than a 10,000-row keyword export.

4. Surfer — best for finding gaps inside an article

Surfer is more useful once you've identified a target topic.

Instead of asking "What topics should we create?", you're asking:

"Our competitor's page ranks #2. What concepts/subtopics does it cover that our page doesn't?"

That's valuable for turning competitor research into content briefs and improving existing pages.

5. Clearscope — best for editorial teams

Clearscope is particularly attractive if your agency has writers/editors producing a high volume of SEO content. Its strength is less "find every competitor gap on the internet" and more make sure the article adequately covers the relevant concepts identified from the SERP.

But there's a more interesting strategy

If your specific goal is:

"Find topic clusters that competitors haven't covered."

Don't simply run a traditional Content Gap report.

Traditional gap analysis finds competitor coverage you lack. It doesn't inherently find white-space that nobody in the competitive set covers.

I'd use a 3-layer analysis:

Layer 1 — Competitor overlap

Find keywords/topics where 2–5 competitors rank but the client doesn't.

→ establishes proven demand.

Layer 2 — Competitor divergence

Find topics covered by only one competitor, or where competitors have very shallow coverage.

→ identifies emerging/niche opportunities.

Layer 3 — Market white space

Combine keyword/topic research, SERP analysis, customer questions, Reddit/forums, Google's related queries, and AI-search prompts.

→ identify clusters where search demand exists but the competitive content landscape is weak.