How to Check What Tracking a Website Uses

Olamide Sule, founder of Dolphin Analytics: a digital analytics expert based in London delivering solutions for agency and in-house clients.

You can read the entire tracking stack of almost any website from your own browser, because the tags run client-side where anyone can see them. That’s useful two ways: checking a competitor’s or prospect’s site to see what they measure and where they advertise, and checking your own before a pitch or a migration to confirm the right tags fire. This walks through four methods, from a ten-second source check to a full-site scan, and shows the exact signatures to look for.

What counts as “website tracking”?

Website tracking is the set of scripts a site loads to record what visitors do and feed that behaviour to analytics and advertising platforms. In practice it means three things: an analytics tool (usually GA4), a tag manager that loads and controls the rest (usually Google Tag Manager), and one or more advertising pixels (Meta, Google Ads, TikTok, LinkedIn). Each one leaves a fingerprint in the page, either a named script file or a network request to a known domain.

Those fingerprints are what you look for. You don’t need access to the site, an account, or any special tool to read them, because the browser downloads and runs every tag in front of you.

How do you check what tracking a website uses?

To check what tracking a website uses, inspect the page from the visitor’s side with one of four methods: read the page source for tag signatures, watch the browser network tab for tracking requests, run a detection extension, or scan the whole site with a tracking checker. The network tab and a scanner are the most reliable, because they capture tags that Google Tag Manager injects after the page loads. All four work on any public site.

Pick the method by how much you need. A quick “do they run Meta ads?” check is a ten-second source search. A full “what’s their entire stack and is it firing correctly?” question wants the network tab or a scan.

Method 1: Read the page source (fastest first look)

Press Ctrl+U (Cmd+Option+U on a Mac) to open the raw HTML, then Ctrl+F to search it. Type the signature you care about: “gtag” for Google tags, “GTM-” for a Tag Manager container, “fbq” or “connect.facebook.net” for the Meta Pixel, “ttq” for TikTok. A match tells you the tag is hardcoded into the page, and often shows the ID right next to it.

The limit is real: view-source shows only the HTML the server sent, before any JavaScript runs. A site that loads one Google Tag Manager container and lets GTM inject everything else will show the GTM snippet and almost nothing else. So a clean source search rules a tag in, never fully out. When the source looks bare, move to the network tab.

Method 2: Watch the browser network tab (what actually fires)

Open DevTools (F12, or right-click and choose Inspect), select the Network tab, then reload the page with it open. Every request the page makes appears in the list, including the ones GTM fires at runtime. Filter the list to cut the noise: type “collect” to find GA4 hits, “facebook” for the Meta Pixel, “google-analytics” for any Google Analytics traffic, “tiktok” or “linkedin” for those pixels.

This is the ground truth. The Network tab shows what genuinely sends data, not just what’s written in the HTML, so it catches GTM-injected tags that view-source misses and confirms a tag is firing rather than just present. It’s also how you spot a tag firing twice, a common fault that inflates numbers. For your own site, that same view is the first check when GA4 shows no data: if no request to google-analytics.com/g/collect appears on load, the tag isn’t firing at all.

Method 3: Run a detection extension (one-click reads)

Browser extensions turn tag detection into a single click, each covering a slice of the stack:

• Google Tag Assistant (tagassistant.google.com) verifies Google tags, GA4 and GTM, and shows whether they fire correctly on the page you’re on.
• Meta Pixel Helper lights up on any page carrying a Meta Pixel and shows the pixel ID and the events it sends.
• Ghostery and its WhoTracks.Me project list every tracker on a page, advertising, analytics and social, which is handy for a broad “who’s on this site” read.
• Omnibug decodes analytics and marketing requests in the DevTools panel, useful when you want the request parameters rather than only the tag name.

The tradeoff: each extension covers one corner, so a full picture means installing several, and they only report the single page open in your browser. For one page and one platform they’re the quickest option going.

Method 4: Scan the whole site with a tracking checker

A tracking checker takes a URL, crawls the site from the outside the way a visitor’s browser sees it, and returns every tag it finds across the pages it reaches. That’s the fastest route to a full stack, and the only one that covers a whole site rather than the single page you have open. It also needs nothing installed, which matters when you’re checking a site on someone else’s machine or on mobile.

Sonar is our free version: paste a URL and it reports whether GA4 is present and firing, the Google Tag Manager and measurement IDs it found, the ad pixels running, and the dataLayer and consent setup, then flags problems it can prove from the crawl. It works from outside with no account and nothing to install, so it reads a competitor’s site as easily as your own.

How do you check for a specific tag?

Each platform loads a named script and calls a known domain, so once you know the signature you can confirm any single tag in seconds. Search the page source for the script, or filter the Network tab for the domain:

Tag	Script or signature in source	Network request domain	ID format
GA4 (Google Analytics 4)	googletagmanager.com/gtag/js, “gtag(“	google-analytics.com/g/collect	G-XXXXXXXXXX
Google Tag Manager	googletagmanager.com/gtm.js	googletagmanager.com	GTM-XXXXXXX
Meta (Facebook) Pixel	connect.facebook.net/en_US/fbevents.js, “fbq(“	facebook.com/tr	numeric, in fbq(‘init’, …)
Google Ads	”gtag(” with an AW- ID	googleadservices.com/pagead/conversion	AW-XXXXXXXXX
TikTok Pixel	analytics.tiktok.com, “ttq.”	analytics.tiktok.com	alphanumeric
LinkedIn Insight Tag	snap.licdn.com	px.ads.linkedin.com	numeric partner ID
Microsoft Clarity	clarity.ms/tag	clarity.ms	short alphanumeric
Hotjar	static.hotjar.com	script.hotjar.com	numeric site ID

One note on old tags: a request to google-analytics.com/collect with a UA- prefixed ID points at Universal Analytics, which Google switched off in July 2023. If you still see one, it’s a dead tag collecting nothing, worth mentioning to whoever owns the site.

What can you learn from a competitor’s tracking setup?

A competitor’s tags tell you where they spend and how they measure, without a single data point of theirs. A Meta Pixel and a TikTok Pixel say they run social ads; a Google Ads conversion tag says they bid on search; a LinkedIn Insight Tag points at B2B. A Google Tag Manager container with a long list of tags suggests a mature setup, while a bare GA4 tag on its own suggests a lighter one. Retargeting pixels tell you they’re chasing return visitors.

What you can’t see is their data, their conversion values, or how the tags are configured behind the scenes. Reading a stack shows you the tools on the shelf, not how well they’re used, which is exactly the gap that matters most when you turn the same check on your own site.

The tracking worth checking most is your own

Scanning a competitor is quick to do and genuinely useful for a pitch. The higher-value move is running the same check on your own site, because that’s where the gaps cost money: a pixel firing twice and inflating conversions, consent settings quietly blocking a chunk of EU and UK traffic, or a conversion tag that stopped firing after a redesign. These faults hide in the same Network tab and scan output you’ve just learned to read. The Shopify GA4 and GTM setup guide walks through what a correct stack looks like on one common platform.

Start with a free scan of your own site to see what’s installed and what’s firing, then, if the report surfaces something off, that’s what the free audit is built to run down: whether the numbers you report actually match what happened in the business.