ChatGPT answers, unedited

If your main goal is competitive intelligence on rivals’ Google Search ads, I’d narrow it to SpyFu vs. Semrush.

My recommendation

1. SpyFu — best for pure Google Ads “ad spying”

This would be my first choice if you specifically want to answer:

• What keywords is my competitor bidding on?
• What ads have they run historically?
• Which messaging/offer variations have they repeatedly used?
• Which landing pages are they sending traffic to?
• Who are their biggest paid-search competitors?
• Roughly how much are they spending?
• When did they start/stop targeting particular keywords?

SpyFu has a particularly deep historical ad archive and lets you reverse-search ads to the keywords that triggered them. Its current site says it has historical ad data going back roughly two decades. www.spyfu.com

2. Semrush — best if you want broader competitive intelligence

Semrush's Advertising Research is excellent for seeing competitors' paid keywords, live ad examples, estimated traffic/spend, competitors, landing pages and historical trends. It also lets you analyze different countries and devices. www.semrush.com

I'd choose Semrush if you're doing SEO + PPC + content + market research rather than just Google Ads intelligence.

Quick comparison

One important caveat: neither tool gives you a literal inside view of a competitor's Google Ads account. Their estimates are built from observed/search-result data and modeling. SpyFu, for example, says it captures Google SERPs and records the ads, advertiser, copy and landing page, then derives metrics such as estimated clicks and budget. help.spyfu.com

If I were building a serious competitor-intelligence stack

I'd actually use:

SpyFu → Google Ads Transparency Center → Semrush

Use SpyFu for the historical "what have they been doing?" analysis, Semrush for broader market/SEO/PPC overlap, and Google's own transparency data as an additional source for what advertisers are currently running.

If you tell me your industry and roughly how many competitors you want to monitor, I can also recommend the best tool + subscription tier and a practical competitor-spying workflow (including exactly what metrics I'd track each week).

If your goal is competitive intelligence specifically around rivals’ Google Search Ads, I’d prioritize PPC-focused tools over general “spy” platforms. No tool can see a competitor’s exact bids, Quality Scores, conversion rates, or private account data, but these can estimate keywords, ad copy, landing pages, spend, and history. Semrush SpyFu

My recommendations

What I’d pick by scenario

If you mainly want to “see what competitors are bidding on”

Pick SpyFu.
Use it to answer:

• Which keywords are they buying?
• How long have they been running those ads?
• What ad copy keeps appearing?
• Which competitors overlap with you? SpyFu

If you run an agency or growth team

Pick Semrush.
You get PPC intelligence plus:

• SEO competitor analysis
• keyword gap analysis
• content research
• traffic estimates
• reporting workflows Semrush

If you are trying to beat one specific rival

I’d use a stack:

1. SpyFu → historical Google Ads intelligence
2. Semrush → broader market view
3. Google Ads Transparency Center → verify current advertiser creatives directly from Google’s ecosystem Surfside PPC

My practical shortlist

• Solo marketer / small business: SpyFu
• PPC specialist: SpyFu + Google Ads Auction Insights
• Agency: Semrush
• Enterprise competitive intelligence: Semrush + Similarweb
• E-commerce brand watching many channels: Similarweb + ad intelligence tools

One caution: treat estimated spend and traffic numbers as directional, not exact. The most valuable signals are usually keyword overlap, ad messaging patterns, offer structure, and landing page strategy, not the spend estimates themselves. nordsteg.at

If you tell me your market (e.g., SaaS, local services, ecommerce, finance) and monthly ad spend, I can narrow this down to the best tool stack.

If your main goal is competitive intelligence + seeing what rivals are doing with Google Search Ads, I’d shortlist these:

🥇 If you're specifically trying to “spy” on Google Search Ads: SpyFu

I'd start with SpyFu. It is unusually focused on PPC competitor research: you can enter a rival's domain and investigate their paid keywords, estimated spend/clicks, ad copy, ad history, and competing advertisers. It also lets you identify keywords competitors buy that you don't. SpyFu SpyFu

A particularly useful feature is the historical view. Rather than just asking “what ads are they running today?”, you can see which keywords and ad messages they've continued using over time. That's much more useful for distinguishing a serious strategy from a random experiment. SpyFu

🥈 Semrush if you want a complete CI stack

Semrush would be my choice if you're doing more than PPC.

Its Advertising Research can show competitor paid keywords, ad copy, position changes, competing domains, historical activity, and landing pages. It can also combine that with SEO, Shopping, and broader competitive research. Semrush Semrush

The big advantage is that you can answer questions like:

“Competitor X is spending heavily on these keywords—but are they also dominating organic search, Shopping, and other channels?”

That's considerably more powerful than an isolated PPC spy tool.

One important caveat

None of these tools literally sees a competitor's private Google Ads account. They're reconstructing competitive intelligence from observed/search-indexed advertising data and estimates. Semrush explicitly notes that paid-search data can differ from the advertiser's actual Google Ads data because ads can vary by location, time, audience, keyword coverage, etc. Semrush

So I would not treat estimated competitor spend as an exact number. Use it for relative comparisons and trend detection.

What I'd buy

• $ / solo operator: SpyFu
• Marketing team / agency: Semrush
• Serious competitive-intelligence program: Semrush + Similarweb
• Primarily SEO with some PPC research: Ahrefs
• Only care about “what are my competitors bidding on and what ads are they running?”: SpyFu

If you tell me your industry, approximate monthly ad spend, and how many competitors you want to monitor, I can narrow this down to the best 2–3 tools and tell you exactly what I'd use each one for.

I'd start with SpyFu. It is unusually focused on PPC competitor research: you can enter a rival's domain and investigate their paid keywords, estimated spend/clicks, ad copy, ad history, and competing advertisers. It also lets you identify keywords competitors buy that you don't. SpyFu SpyFu

A particularly useful feature is the historical view. Rather than just asking “what ads are they running today?”, you can see which keywords and ad messages they've continued using over time. That's much more useful for distinguishing a serious strategy from a random experiment. SpyFu

🥈 Semrush if you want a complete CI stack

Semrush would be my choice if you're doing more than PPC.

Its Advertising Research can show competitor paid keywords, ad copy, position changes, competing domains, historical activity, and landing pages. It can also combine that with SEO, Shopping, and broader competitive research. Semrush Semrush

The big advantage is that you can answer questions like:

“Competitor X is spending heavily on these keywords—but are they also dominating organic search, Shopping, and other channels?”

That's considerably more powerful than an isolated PPC spy tool.

One important caveat

None of these tools literally sees a competitor's private Google Ads account. They're reconstructing competitive intelligence from observed/search-indexed advertising data and estimates. Semrush explicitly notes that paid-search data can differ from the advertiser's actual Google Ads data because ads can vary by location, time, audience, keyword coverage, etc.

So I would not treat estimated competitor spend as an exact number. Use it for relative comparisons and trend detection.

What I'd buy

If your main goal is competitive intelligence on rivals’ Google Search Ads—keywords, ad copy, landing pages, historical activity, and estimated spend—I’d shortlist these:

🥇 My pick: Semrush

For most businesses, I'd start with Semrush Advertising Research. You can enter a rival's domain and see the paid keywords they're appearing for, ad copy, competitors, landing pages, position changes, and historical advertising trends. Semrush says its historical advertising data goes back as far as 2012. www.semrush.com

Its current Advertising plans are $99/mo annually for Base and $220/mo annually for Pro; Pro adds broader competitor-ad intelligence and display/video/social analysis. www.semrush.com

What I'd actually do with it:

1. Put in 5–20 competitors.
2. Export their paid keywords.
3. Identify keywords where multiple rivals are bidding.
4. Look at the ads they've kept running for months/years.
5. Compare their messaging and offers.
6. Examine the landing pages receiving paid traffic.
7. Find keywords where they're spending but you aren't.
8. Track newly appearing advertisers.

That's much more useful than simply looking at what ads happen to show up in Google today.

🕵️ SpyFu is particularly good if you mean "spy on their ads"

SpyFu is arguably the more focused choice if your question is literally “What Google Ads has this competitor been running?”

Its Ad History provides historical competitor ad copy, keywords, landing pages, and changes over time. SpyFu currently claims coverage going back 18–20 years depending on the report. www.spyfu.com

It also lets you reverse-search ads to find the keywords that trigger them and identify advertisers competing on particular keywords. www.spyfu.comhelp.spyfu.com

One particularly useful feature is seeing which advertisers have appeared on a particular keyword over time. That's excellent for discovering competitors you didn't even know about. www.spyfu.comhelp.spyfu.com

📊 Similarweb

I'd consider Similarweb if you're doing serious market intelligence rather than just PPC research. Its Search Ads Analytics includes competitor ad creative, position, estimated impressions, and traffic share from specific ads. www.similarweb.com

It's especially interesting when you want to answer questions like:

"Who is taking traffic from my competitors, and how important is paid search to their overall acquisition strategy?"

rather than merely:

"What keywords is Competitor X bidding on?"

One important caveat

None of these tools actually gives you your competitor's Google Ads account data. They're reconstructing competitor activity from observed/search-indexed data and modeling. For example, Semrush explicitly says its paid-traffic numbers are estimates for competitive benchmarking, not the competitor's actual spend, and that local, time-specific, audience-targeted, and otherwise uncaptured ads can be missed. www.semrush.com

SpyFu similarly describes its methodology as repeatedly capturing Google SERPs and recording advertisers, ad copy and landing pages, from which it derives estimates such as clicks and budget. help.spyfu.com

My recommendation by situation

• One tool for everything: Semrush
• Primarily Google Ads competitor research: SpyFu
• Enterprise-level market/traffic intelligence: Similarweb
• SEO is equally important: Semrush or Ahrefs
• Small business wanting inexpensive PPC intel: SpyFu

If you tell me what industry you're in, roughly how much you spend on Google Ads per month, and whether you're B2B or B2C, I can recommend the specific tool + plan I'd buy and show you exactly how I'd use it to reverse-engineer 5–10 competitors.

If by “spying” you mean legitimately researching competitors’ publicly observable Google Search ads, keywords, messaging, and strategy, there are several good options. You won't get their actual Google Ads account data, but you can get surprisingly useful estimates and historical observations.

My ranking

1. SpyFu — my pick if Google Ads is the priority

SpyFu's PPC research tools let you enter a competitor's domain and investigate the keywords they're associated with, their ad copy, historical activity, estimated clicks/spend, and competing advertisers. Its historical ad archive is particularly useful for seeing which messaging competitors have kept running versus abandoned. www.spyfu.com

I'd use it to answer questions like:

• What keywords is Competitor X bidding on?
• Which high-value keywords are they apparently prioritizing?
• What headlines/descriptions have they tested?
• How has their messaging changed over 6–24+ months?
• Which competitors are appearing alongside us?
• What keywords do competitors buy that we don't?
• Are they entering or abandoning particular markets?

If your primary objective is “show me what my competitors are doing in Google Search,” I'd start here.

2. Semrush — better if you want a complete competitive-intelligence stack

Semrush Advertising Research is excellent for identifying paid-search competitors, keyword overlap, ad copy, position changes, and estimated paid traffic. www.semrush.com

I'd choose Semrush over SpyFu if you're also doing:

• SEO competitor analysis
• backlink research
• keyword-gap analysis
• content research
• market/competitor tracking
• broader digital marketing analysis

In other words, SpyFu = PPC intelligence specialist; Semrush = broader marketing intelligence platform.

One important caveat: Semrush explicitly says its paid-traffic and spend figures are benchmarks/estimates rather than your competitors' actual Google Ads spend. Search results can also vary by geography, time, audience, and keyword coverage. www.semrush.com

3. Similarweb — use it to understand the bigger picture

Similarweb is less about “show me every ad this competitor ran” and more about “how does this competitor acquire traffic?”

It's useful for figuring out whether a rival's growth appears to be coming from:

Paid Search → Organic → Direct → Referral → Social → Display

That makes it a good second tool alongside SpyFu/Semrush rather than a replacement.

The free tool I'd absolutely use

Google's Ads Transparency Center is worth checking before paying for anything. It gives you Google's own view of ads from advertisers, rather than a third-party estimate.

For serious competitive research, I'd actually combine:

Google Ads Transparency Center + SpyFu + Semrush

That gives you:

1. Actual observable Google ad creatives
2. Historical PPC/keyword intelligence
3. Competitor discovery + SEO/market context

And I'd treat estimated spend/traffic from any third-party platform as directional, not as an exact number. Semrush itself notes that no provider can capture every volatile Google SERP/ad impression perfectly. www.semrush.com

If you tell me your industry and roughly how many competitors you want to monitor (e.g. 5, 20, or 100), I can recommend the most cost-effective stack and exactly what I'd monitor each week.

If your main goal is competitive intelligence around Google Search Ads, I’d narrow the field to Semrush, SpyFu, and Google’s own Ads Transparency Center.

🥇 My recommendation: Semrush

Semrush

I'd pick Semrush if you're doing this professionally. Its advertising research can help you investigate competitors' paid keywords, ad copy, landing pages, estimated traffic/spend and competitive overlap, while also giving you SEO intelligence in the same platform. Recent 2026 comparisons consistently put it near the top for combined SEO/PPC competitive intelligence. www.analook.com

The big advantage is that you aren't just asking "what ad are they running?" You can investigate:

• What keywords they're bidding on
• Which competitors overlap with them
• Their ad messaging
• Landing pages they're sending traffic to
• Which keywords appear strategically important
• Changes in their paid-search strategy
• Paid vs. organic positioning

🥈 SpyFu — if Google Ads is the primary mission

SpyFu

If you specifically mean "I want to reverse-engineer my competitors' PPC programs", I'd seriously consider SpyFu.

Its strength is historical competitive PPC data. Current comparisons highlight its long PPC history and competitor keyword/ad research, while also noting that it's considerably cheaper than Semrush. blog.hubspot.com

I'd choose SpyFu over Semrush when:

"I care much more about competitor Google Ads than I care about having an all-purpose marketing platform."

🆓 Don't overlook Google's own tool

Google Ads Transparency Center

This is particularly useful because it's Google's own public database of ads. You can search by advertiser or website and filter for Search ads. Google says the platform contains ads shown since September 4, 2023 when using the platform filter. adstransparency.google.com

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

The combination is powerful:

Google Transparency Center → what they're actually running
SpyFu/Semrush → keywords, history, competitive positioning
Similarweb → traffic sources and market context

If I were building a competitor-spying stack

Solo marketer / small business:
SpyFu + Google Ads Transparency Center

Serious PPC team:
Semrush + Google Ads Transparency Center

Competitive intelligence / strategy team:
Semrush + Similarweb + Google Transparency Center

Enterprise CI:
Add something like Crayon or Klue for broader competitor monitoring, pricing/product changes and sales battlecards; those are a different category from PPC intelligence. blog.hubspot.comcloro.dev

One important caveat: these platforms don't give you your competitor's actual Google Ads account data. Spend, bids, conversions, ROAS, exact targeting and other private account information aren't publicly available. Third-party tools are making estimates/inferences from observed data.

If you tell me what kind of business you're competing in (e.g. SaaS, local services, ecommerce, agency) and roughly how much you're willing to spend per month, I can recommend the exact stack and explain how I'd use it to reverse-engineer 3–5 competitors' Google Ads campaigns.

If your main goal is competitive intelligence on rivals' Google Search Ads, I’d narrow it to Semrush vs. SpyFu, with a few specialized tools depending on how broad your intelligence needs are.

My picks

1. Semrush — best overall

Semrush Advertising Research is probably what I'd buy if you want one competitive-intelligence platform.

You can enter a rival's domain and investigate:

• Keywords they're bidding on
• Estimated paid traffic and spend
• Their paid-search competitors
• Current/live ad copy
• Historical ad activity
• Landing pages receiving paid traffic
• Changes in their paid keyword portfolio
• Desktop vs. mobile
• Different countries/markets

Semrush says its historical Advertising Research data goes back as far as 2012, which is particularly useful for figuring out what competitors have repeatedly tested versus what they're only experimenting with. www.semrush.com

Why I prefer it: you can go from "What ads is this competitor running?" → "What keywords are they targeting?" → "Who else competes with them?" → "What landing pages are they sending traffic to?" in one ecosystem.

2. SpyFu — best specifically for "spying" on PPC

SpyFu PPC Research is arguably the more purpose-built choice if your question is literally:

"What have my competitors been doing with Google Ads?"

SpyFu emphasizes historical PPC data, including competitors' paid keywords, ad history, ad tests, estimated clicks/spend, and competitors bidding on the same terms. www.spyfu.com

One particularly interesting feature is its ad history: SpyFu says it records Google SERPs and captures the ads, advertiser, ad copy, and landing page, allowing it to reconstruct historical advertising activity. help.spyfu.com

It can therefore answer questions like:

• Which keywords has Rival X bought?
• Which ads have they kept running for months?
• What messaging have they tested?
• Which keywords do they buy that we don't?
• Who are their biggest PPC competitors?
• What appears to be their approximate PPC budget?
• What campaigns/keywords have they abandoned?

If PPC is 80%+ of your competitive-intelligence work, I'd seriously consider SpyFu over Semrush.

What I'd actually use

If you're doing serious competitor research, I'd use a two-layer approach:

Semrush + SpyFu

Use Semrush for the big picture:

competitor → paid keywords → competitors → landing pages → SEO → market

Use SpyFu for the historical PPC deep dive:

competitor → keyword history → ad history → ad testing → recurring winners → budget trends

Then use Google's own Ads Transparency Center as a reality check on what Google is actually showing. It's particularly useful for validating current ads rather than relying exclusively on third-party estimates.

One important caveat

None of these tools gives you a secret login to a competitor's Google Ads account. They're reconstructing competitive activity from observed search results and other data sources, so spend, clicks, conversions, and "winning" ads are estimates, not the competitor's actual account data. SpyFu, for example, explicitly describes its budget/click figures as calculated estimates based on its observed SERP data. help.spyfu.com

Bottom line:

• Want one tool: Semrush.
• Want the best PPC spying: SpyFu.
• Want serious CI: Semrush + SpyFu + Google's Ads Transparency Center.
• Want broader market/competitor intelligence beyond PPC: add Similarweb.

If you tell me your industry and roughly how many competitors you want to monitor, I can also recommend the best tool/plan and show you exactly how I'd set up a competitor Google Ads monitoring workflow.

If your main goal is competitive intelligence + seeing what rivals are doing in Google Search Ads, I’d narrow it to Semrush and SpyFu, with Google’s own Ads Transparency Center as a free supplement.

🥇 My recommendation: Semrush

For a business that wants to systematically monitor competitors, I'd start with Semrush. Its Advertising Research lets you investigate competitors' paid keywords, ad copy, positions, estimated traffic/spend, landing pages, and historical changes. You can also identify previously unknown competitors based on paid-keyword overlap. www.semrush.com

That's particularly useful because you're not just asking "what ads are they running?" You're able to build a picture of:

• Which keywords they appear to be buying
• Which keywords they've recently started/stopped targeting
• Their recurring ad messaging
• Their landing pages
• Their estimated PPC investment
• Which competitors overlap with them
• How their paid-search strategy changes over time

Semrush Advertising Research documentation

🕵️ If you specifically want to "spy on Google Ads": SpyFu

I'd seriously consider SpyFu if you're primarily a PPC marketer rather than a broader SEO/CI team.

SpyFu is explicitly built around competitor PPC research and provides paid keywords, estimated spend, competitor comparisons, PPC history, and historical ad copy. Its current site says membership starts around $33/month, making it considerably cheaper to experiment with than a full enterprise CI stack. www.spyfu.com

Its killer use case is something like:

Competitor A → show me the keywords they've historically bought, their ads, how long they've run them, estimated spend, and where our PPC footprints overlap.

That historical dimension is extremely useful because an ad that a competitor has continued running for months is more interesting than an ad you happen to see today.

🔎 Don't overlook Google's own transparency data

For actual creatives, I'd pair either tool with the Google Ads Transparency Center. Semrush itself recommends it for researching Performance Max because PMax doesn't expose the same keyword-level information as traditional Search campaigns. It lets you inspect the creative advertisers are running across Google's properties. www.semrush.com

The important distinction is:

Semrush/SpyFu = inferred competitive intelligence
Google Transparency Center = Google's own record of advertiser creatives

Neither gives you the competitor's actual account data, of course. Spend, targeting, conversion rates, audiences, ROAS, etc. are estimates or unavailable.

What I'd buy

Solo founder / small PPC team:
SpyFu + Google Ads Transparency Center

Serious marketing team:
Semrush + Google Ads Transparency Center

Enterprise competitive-intelligence team:
Semrush + Similarweb, potentially adding a dedicated ad-intelligence platform.

Similarweb becomes valuable when your question changes from "what keywords are they bidding on?" to "how does this competitor acquire traffic overall, who is gaining share, and what does the market look like?" www.similarweb.com

If you tell me your industry and roughly how much you're willing to spend per month ($50, $150, $500, $2k+), I can recommend the exact stack and show you how I'd use it to reverse-engineer 3–5 competitors' Google Ads strategies.

If your goal is competitive intelligence specifically for Google Search Ads (PPC)—seeing what rivals bid on, their ad copy, landing pages, historical campaigns, and estimated spend—I’d shortlist these:

backlinko.comwww.semrush.com

My recommendations by situation

1. You mainly want to “spy” on competitors’ Google Ads
→ SpyFu
It is probably the closest match to your use case: enter a competitor domain and see:

• keywords they have bid on
• ad copy variations
• historical ad activity
• estimated clicks/CPC/spend
• keywords they share with competitors

octolens.com

2. You run a serious PPC program and also care about SEO
→ Semrush
Better if you want a broader intelligence stack:

• competitor paid keywords
• ad positions
• landing pages
• SEO gaps
• traffic analysis
• market research

backlinko.comwww.semrush.com

3. You are an agency managing many clients
→ Semrush + SpyFu combo
A common setup:

• Semrush = market overview and reporting
• SpyFu = digging into competitor PPC history and keyword strategy

4. You want to know “what ads are they running right now?”
Use ad transparency resources too:

• Google Ads Transparency Center — useful for viewing ads from verified advertisers, though it is not a full competitive intelligence database.

What I would not trust blindly

No tool can truly reveal a competitor’s exact:

• daily budget
• conversion rate
• ROAS
• profit margins

Spend and traffic numbers are modeled estimates. Use them to identify patterns, not as ground truth. brndle.com

My practical stack

For most businesses:

1. SpyFu → find winning keywords and ad angles
2. Semrush → understand the broader competitive landscape
3. Google Ads Transparency Center → verify actual creatives

If you tell me your industry (e.g., SaaS, ecommerce, local services, legal, healthcare) and approximate monthly ad spend, I can suggest the best stack and workflow.

If your main goal is competitive intelligence + seeing what rivals are doing with Google Search Ads, I’d shortlist these:

My pick: Semrush

For your specific use case, Semrush would be my first choice. Its Advertising Research product lets you enter a rival's domain and investigate:

• The paid keywords they're bidding on
• Their estimated paid traffic and traffic cost
• Current/live ad copy
• Historical ad activity going back years
• Which competitors overlap with them
• Landing pages receiving paid traffic
• Desktop vs. mobile activity
• Different countries/markets

Semrush explicitly supports historical Google Ads research going back to 2012, which makes it particularly useful for figuring out not just what competitors are running now, but what they've repeatedly tested over time. www.semrush.comwww.spyfu.com

Semrush Advertising Research

If Google Ads spying is the #1 priority: SpyFu

I'd seriously consider SpyFu instead if you care more about PPC than broader competitive intelligence.

It specializes in exactly this: competitor domains → paid keywords → ads → historical PPC activity → estimated clicks/spend. Its current product also lets you compare competitors and identify keywords they're buying that you aren't. www.spyfu.com

One particularly useful feature is its ad history: you can look at ads competitors have tested and identify messaging that has persisted rather than assuming every ad you see is a winner. help.spyfu.com

SpyFu PPC Competitor Research

What I'd actually do

If I were building a serious competitor-monitoring setup:

Semrush + SpyFu is the strongest combination.

Use Semrush for the broad picture:

Who are my competitors? → What keywords do they buy? → What ads/landing pages do they use? → How has their strategy changed?

Then use SpyFu for deeper PPC archaeology:

What have they historically tested? → Which keywords have they consistently bought? → What opportunities are they buying that I don't?

One caveat: these platforms are estimating and reconstructing competitors' advertising activity from their own datasets; they aren't giving you access to the rival's private Google Ads account. So treat spend, clicks, and "best performing" estimates as directional rather than exact. Semrush itself describes these as estimates. www.semrush.com

If you tell me your industry (e.g. SaaS, law, ecommerce, local services) and roughly how many competitors you want to monitor, I can recommend the most cost-effective stack and explain exactly what I'd monitor each week.

If your main goal is competitive intelligence + seeing what rivals are doing in Google Search Ads, I’d shortlist these:

1. Semrush — best all-around choice

Semrush's Advertising Research is particularly strong for what you're describing. You can enter a rival's domain and investigate:

• Paid keywords they're bidding on
• Estimated paid traffic and spend
• Actual/live ad examples
• Ad copy and messaging
• Landing pages receiving paid traffic
• Competitors they're fighting against
• New/lost paid keywords
• Historical advertising activity going back years
• Different countries and devices

Semrush says its historical Advertising Research data goes back to 2012, which makes it useful for figuring out not just what competitors advertise now, but what they've apparently tested and abandoned over time. www.semrush.comwww.spyfu.comhelp.spyfu.comhelp.ahrefs.com

Semrush Advertising Research

I'd choose Semrush if you're building a serious competitive-intelligence process, rather than simply trying to find a competitor's keywords.

2. SpyFu — best if "spy on their Google Ads" is the primary objective

SpyFu is unusually focused on exactly this use case. It provides competitor paid keywords, estimated spend/clicks, ad history, competing advertisers, and historical ad tests. Its current positioning is explicitly around Google Ads/PPC competitive research. www.spyfu.com

One particularly useful capability is seeing which keywords multiple competitors buy, which can help distinguish a strategically important keyword from something one competitor merely tested. help.spyfu.com

SpyFu PPC research

If I had only ~$50/month and cared primarily about Google Search Ads, I'd seriously consider SpyFu before Semrush.

3. Ahrefs — excellent if SEO matters too

Ahrefs has gotten substantially better for paid-search intelligence. Its Site Explorer can show competitor paid keywords, ad copy, paid traffic, landing pages, CPC estimates and changes in advertising strategy over time. help.ahrefs.com

Ahrefs PPC research

I'd pick it when the question is more like:

"Give me a complete picture of how this competitor acquires search traffic."

rather than simply:

"What Google Ads are they running?"

What I'd actually buy

For a startup / growth team:
Semrush + SpyFu is a very powerful combination, although there is some overlap.

For one person primarily doing PPC:
SpyFu.

For an SEO + PPC team:
Semrush or Ahrefs, with Semrush getting my nod if paid advertising is the heavier component.

For serious competitive intelligence:
I'd use Semrush as the core, then supplement it with a broader market-intelligence platform if you also need competitor pricing, website changes, technology stack, traffic sources, product launches, etc.

One important caveat: these tools aren't actually looking inside a competitor's Google Ads account. Their estimates are based on observed search results and proprietary datasets, so spend, clicks, rankings, and "winning" ads are estimates rather than the competitor's first-party data. For example, Semrush explicitly describes traffic/cost as estimates. www.semrush.com

If you tell me your industry, approximate monthly ad spend, and how many competitors you want to monitor, I can narrow this down to the best 1–2 tools and tell you what I'd use for a $100/mo, $500/mo, or $2k+/mo CI stack.

If by “spying” you mean legitimate competitive intelligence on publicly observable Google Search ads, I’d shortlist these:

🥇 My pick: SpyFu

If your primary question is “What are my competitors doing in Google Search Ads?”, I'd start with SpyFu.

It lets you research a rival's domain to uncover:

• Paid keywords they're targeting
• Estimated PPC spend and clicks
• Their current and historical ad copy
• Competitors bidding on the same terms
• Changes in their PPC activity over time
• Keywords you're missing relative to competitors

SpyFu says its PPC database has been expanded substantially in 2026, and its current plans start at $33/month. www.spyfu.com

The particularly useful feature is ad history: rather than just seeing an ad that happens to be running today, you can examine how a competitor's messaging has evolved. www.spyfu.com

🥈 Semrush if you want a complete CI stack

I'd choose Semrush if you want to go beyond PPC into SEO, Shopping, landing pages, keyword gaps, etc.

Its Advertising Research product lets you see competitor paid keywords, ads, historical trends, competitors and landing pages. www.semrush.com

Its current Advertising Toolkit pricing lists $99/month for Base and $220/month for Pro when billed annually; Pro adds broader competitor-ad intelligence through AdClarity. www.semrush.com

One important caveat: none of these tools literally sees your competitor's Google Ads account. They're reconstructing competitor activity from observed SERPs and their own datasets. Semrush explicitly notes that its paid-traffic figures are estimates and that local, time-specific, audience-targeted and otherwise uncaptured ads can be missed. www.spyfu.comwww.semrush.com

🥉 Similarweb for serious competitive intelligence

If you're trying to answer questions like:

“How is this competitor allocating its entire digital marketing budget?”

rather than simply:

“What Google keywords are they bidding on?”

I'd look at Similarweb. Its Ad Intelligence covers search, display, social and GenAI advertising, including competitor campaigns, creatives and estimated spend/trends. support.similarweb.com

What I'd actually buy

Small business / agency: SpyFu
Performance marketing team: Semrush
Large company / market intelligence team: Similarweb
Very serious PPC competitor research: SpyFu + Semrush — they overlap, but their datasets and interfaces can give you different views of the same competitor.

If you tell me your industry, approximate monthly Google Ads spend, and how many competitors you want to monitor, I can narrow this down to the best tool and plan for you.

If your main goal is competitive intelligence + seeing what rivals are doing with Google Search Ads, I’d narrow it to Semrush vs. SpyFu.

My recommendation: Semrush

Semrush Advertising Toolkit

I’d choose Semrush if you want a broader competitive-intelligence platform rather than just an ad-spying tool. Its Advertising Research lets you investigate a competitor’s:

• Paid keywords and positions
• Current ad copy
• Historical ad activity going back to 2012
• Competitors bidding on the same terms
• Landing pages receiving paid traffic
• Estimated paid-search traffic and spend www.semrush.comwww.spyfu.com

It also covers Google Shopping, Meta, display, video and social, so you can expand beyond Search Ads when needed. www.semrush.com

Best specifically for "spy on their Google Ads": SpyFu

SpyFu

SpyFu is probably the one I'd test first if your question is essentially "What keywords are my competitors buying, what ads are they running, and how has that changed?"

It specifically exposes competitor PPC keywords, estimated budgets, ad history, ad copy, PPC competitors and changes over time. SpyFu says its PPC database covers 7.2 trillion results across 152 million domains, with monthly rollups updated in July 2026. www.spyfu.com

How I'd choose

One important caveat: none of these tools literally sees a competitor's Google Ads account. They infer/collect what appears in search results and model things such as spend, traffic and keywords. Semrush explicitly notes that its paid-traffic estimates are benchmarks rather than the competitor's actual Google Ads spend, and that local, time-specific and audience-targeted ads can escape its dataset. www.semrush.com

If I were spending my own money: I'd start with SpyFu for PPC-focused intelligence, or Semrush if competitive intelligence is part of a larger SEO/marketing operation.

If you tell me your industry and roughly how many competitors you want to monitor, I can also tell you which one I'd buy—and whether there are better specialist tools like iSpionage, Similarweb, or Adbeat for your particular use case.

If your main goal is competitive intelligence around rivals’ Google Search Ads, I’d shortlist these:

🥇 My recommendation: SpyFu

If by "spying" you specifically mean:

• Which keywords competitors are buying
• Their historical Google Ads
• Ad copy they've tested
• Which ads appear to have persisted
• Estimated PPC traffic and spend
• Competitors bidding on the same terms
• Keywords your competitors buy that you don't

…I'd start with SpyFu. Its current product specifically emphasizes competitor Google Ads history, ad tests, paid keywords, estimated clicks/spend, and finding keywords competitors buy that you don't. www.spyfu.comwww.spyfu.com

SpyFu currently advertises plans starting around $33/month, which also makes it relatively easy to test without committing to an expensive enterprise platform. www.spyfu.comwww.spyfu.com

🥈 Semrush if you want a broader intelligence platform

I'd choose Semrush if you want PPC intelligence plus SEO, content, competitor discovery, Shopping, and broader marketing research.

Its Advertising Research can show competitors' paid keywords, ad examples, estimated traffic/cost, position changes, landing pages, and historical advertising activity going back to 2012. www.spyfu.comwww.spyfu.comwww.semrush.comvi.semrush.com

One particularly useful feature is its Paid Competitors report: it identifies domains competing for overlapping paid keywords and lets you compare keyword coverage, estimated paid traffic, and traffic cost. www.semrush.com

Important caveat

None of these tools literally has access to your competitors' private Google Ads accounts. They're reconstructing competitive intelligence from observed/search-indexed advertising data. Consequently, spend, clicks and keyword coverage are estimates, and even Semrush explicitly warns that its figures won't perfectly match actual Google Ads data. Local, highly targeted, audience-specific, or time-sensitive ads can be missed. vi.semrush.com

So I wouldn't treat "Competitor spends $47,000/month" as gospel. I'd treat it as directional intelligence.

If I were building a serious competitor-monitoring setup

I'd use:

SpyFu → Google Search → Semrush → your own analytics

Use SpyFu to identify what competitors have historically tested, Google Search to see what they're actually showing right now, and Semrush to understand the broader competitive landscape.

If you tell me what industry you're in, roughly how much you spend on Google Ads, and how many competitors you want to monitor, I can recommend the most cost-effective stack (including whether you actually need Semrush/SpyFu or something more specialized).