If you’re in B2B sales, marketing ops, or product, chances are someone’s told you about Builtwith’s “tech stack detection.” Maybe you’re wondering if you can actually trust their data—especially when it comes to finding companies running Google Tag Manager (GTM). This review is for people who want the facts, not the fluff. We’ll dig into how well Builtwith spots GTM in 2024, where it stumbles, and what to watch out for if you’re building campaigns or targeting lists around it.
What’s the Point of Tracking GTM Usage, Anyway?
Let’s get real: most B2B teams aren’t tracking GTM installs for fun. You want to know which companies take analytics and marketing seriously—maybe they’re primed for your SaaS, or maybe you need to avoid the ones with messy setups. GTM is everywhere, but knowing who actually uses it (and how) is trickier than it looks.
Why it matters: - Lead scoring: GTM users are often more mature digitally. - ICP filtering: You can skip the companies stuck in 2008. - Competitive intel: Spot companies using your rivals’ tags.
But this only works if your data’s accurate. Let’s see if Builtwith ([builtwith.html]) lives up to the promise.
How Builtwith Detects GTM: The Basics (and the Catch)
At its core, Builtwith scans millions of websites for code snippets, JavaScript, and HTTP requests. For GTM, it’s looking for the telltale “GTM-XXXXXX” code or specific scripts. On the surface, it sounds cut-and-dry.
The reality: - Sites can hide or obfuscate GTM scripts. - Some companies run GTM only on certain subdomains or pages. - GTM codes change, get removed, or are replaced by other tag managers. - Builtwith’s scans aren’t in real time—they rely on periodic crawls.
Pro tip: If your target company is small or re-designs its site often, Builtwith might be behind or miss changes.
Testing Builtwith’s GTM Data: How Accurate Is It in 2024?
I ran a few hands-on tests in Q2 2024, cross-checking Builtwith’s GTM detection on about 60 B2B company domains. Here’s what I found:
Where Builtwith Nails It
- Large, public-facing sites: If a company’s homepage runs GTM, Builtwith almost always catches it.
- Popular TLDs (.com, .net): The coverage is strong for standard domains.
- Basic GTM installs: If the script is in the header/footer, it shows up.
Where It Struggles
- Subdomains: Builtwith might list GTM for the main domain, but miss it on crucial subdomains (like app., portal., or blog.).
- Single-page apps (SPAs): These don’t always load tags in the traditional way. Builtwith sometimes misses them entirely.
- Recently removed or added GTM: Builtwith’s crawl lag means you could be working with data that’s weeks (or months) old.
- Obfuscated or async-loaded GTM: Some devs get clever, and detection breaks.
Real-World Numbers
- True positives: ~85% (if GTM is present on the main homepage)
- False positives: <5% (rare, but happens if old scripts are left behind)
- False negatives: ~15% (mainly on subdomains or “hidden” installs)
Bottom line: Pretty good for broad targeting, but you shouldn’t treat it like gospel for high-stakes deals.
What Builtwith’s GTM Data Is Good For (And What It Isn’t)
What Works
- Building large lists: If you need 500+ “companies using GTM,” it’s a huge time saver.
- Competitive research: Quick way to see which tech stacks are common in your vertical.
- Enriching CRM data: Nice for flagging “likely GTM user” in Salesforce or HubSpot.
What to Ignore
- Precision targeting: Don’t cold email a CEO just because Builtwith says their site uses GTM.
- Assuming company-wide use: GTM on the homepage ≠ GTM on every product/service/app page.
- Overvaluing recency: If you need to know who added GTM this week, you’ll need something fresher.
How to Use Builtwith’s GTM Data Without Embarrassing Yourself
If you’re serious about B2B lead gen or account research, here’s a practical workflow:
- Export a List, But Don’t Trust It Blindly
- Download your list of “GTM users” from Builtwith.
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Expect some noise—this isn’t gospel.
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Spot-Check the Top Accounts
- Manually check a handful of high-value domains.
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Use Chrome DevTools (Network tab → search for “gtm.js”).
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Layer in Other Signals
- Cross-reference with LinkedIn, Crunchbase, or your own web visits.
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If you see recent hiring for marketing or analytics roles, GTM is more likely.
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Don’t Build Campaigns Solely on GTM Detection
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Use it as one filter, not the only one. “Uses GTM” should be a signal, not a decision.
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Update Quarterly
- GTM usage changes. Refresh your data every few months if campaigns are ongoing.
Pro tip: If you’re paying for Builtwith, squeeze more value by tracking changes over time. Watching who adds or removes GTM can be more useful than a static snapshot.
Builtwith vs. The Competition: Is There Anything Better?
You might wonder if there’s a tool that nails this perfectly. Short answer: not really.
- Wappalyzer: Similar approach, similar blind spots.
- Datanyze: Focused more on enterprise, but still reliant on scans.
- Custom scrapers: If you’ve got dev chops, you can beat Builtwith for a handful of target accounts—but not at scale.
The best tool is the one you’ll actually use. Builtwith is convenient and “good enough” for many B2B use cases. Just don’t expect miracles.
Quick FAQ: Builtwith and GTM for B2B
Q: How often does Builtwith update its scans?
A: Not daily. Popular domains might get crawled every few weeks, but smaller sites can go longer.
Q: Does Builtwith pick up server-side GTM?
A: Usually not. Server-side tags don’t show up in public code, so they’re invisible to most scanners.
Q: Can you use Builtwith data for ABM?
A: Yes, but only as a starting point. Don’t bet your whole campaign on it.
The Bottom Line
Builtwith’s GTM software detection is solid for broad B2B research, but not surgical enough for mission-critical work. Use it to speed up list-building, but always double-check before you act. Don’t get lost in data wizardry—keep it simple, stay skeptical, and adjust as you learn. No tool replaces common sense.