Website Tracking Checker: Scan Any Site Free

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

A website tracking checker answers one question fast: what is actually tracking visitors on this site? Paste a URL and it reads the tags, pixels and trackers the page loads, from GA4 and Google Tag Manager to the Meta Pixel and ad trackers, without you installing anything or logging into an account. We built one: Sonar is our free tracking checker, made by the team that fixes tracking for clients most weeks. This page covers what a tracking checker detects, how to run one on any site (yours, a prospect’s or a competitor’s), and how to read the report it gives back.

What is a website tracking checker?

A website tracking checker is a tool that loads a URL the way a visitor’s browser would, then reports the tracking scripts it finds on the page. That means the analytics tool (usually GA4), the tag manager that loads and controls the rest (usually Google Tag Manager), and any advertising pixels (Meta, Google Ads, TikTok, LinkedIn). Each tag leaves a fingerprint, and the checker’s job is to find every one and tell you what it is.

The reason a checker works on any public site is that tracking runs client-side. The browser downloads and runs every tag in front of the visitor, so a scanner reading the same page sees exactly what a real visitor’s browser sees. You need no access, no account, and no cooperation from the site owner.

What does a website tracking checker detect?

A good checker detects the analytics tag, the tag manager, and every ad and behaviour pixel on the page, plus the IDs that identify each one. GA4 shows up as a G- measurement ID, Google Tag Manager as a GTM- container, the Meta Pixel as a numeric ID passed to fbq('init', ...). Below the headline tags, it also surfaces the consent and dataLayer setup that decides whether those tags are even allowed to fire.

Here is what shows up on most sites, and the signature a checker keys on:

Tag	What it does	Signature it leaves	ID format
GA4 (Google Analytics 4)	Web and campaign analytics	Request to google-analytics.com/g/collect	G-XXXXXXXXXX
Google Tag Manager	Loads and controls other tags	Loads googletagmanager.com/gtm.js	GTM-XXXXXXX
Meta (Facebook) Pixel	Ad tracking and retargeting	Loads connect.facebook.net, calls facebook.com/tr	numeric, in fbq('init', ...)
Google Ads	Search and display conversion tracking	gtag with an AW- ID	AW-XXXXXXXXX
TikTok Pixel	Social ad tracking	Loads analytics.tiktok.com, calls ttq.	alphanumeric
LinkedIn Insight Tag	B2B ad tracking	Loads snap.licdn.com	numeric partner ID
Microsoft Clarity	Session recording and heatmaps	Loads clarity.ms/tag	short alphanumeric
Hotjar	Session recording and surveys	Loads static.hotjar.com	numeric site ID

One tag worth spotting is a dead one. A request to google-analytics.com with a UA- prefixed ID points at Universal Analytics, which Google switched off in July 2023. If a checker still finds one, it is a tag collecting nothing, worth flagging to whoever owns the site.

How do you check a website for trackers with Sonar?

To check a website for trackers, paste the URL into a scanner and read the report. Sonar is Dolphin Analytics’ free website tracking checker: it crawls the site from the outside, the way a visitor’s browser sees it, and reports the tags it can detect, then flags the problems it can prove from the scan. It needs no account and nothing installed, so it reads a competitor’s site as easily as your own.

The run is three steps:

1. Paste the URL. Give Sonar the page you want to check, your homepage, a product page, a landing page, or a competitor’s site.
2. Run the scan. Sonar loads the page, watches what fires, and collects the tags, IDs, dataLayer and consent signals it sees.
3. Read the report. You get the analytics tag and whether it is firing, the GTM container and measurement IDs, the ad pixels running, the consent setup, and a list of issues the scan can prove.

Prefer to check by hand? The same signatures are readable in your own browser. Our guide on how to check what tracking a website uses walks through the page source, the Network tab and the detection extensions, and where each manual method stops short of a scan.

How do you read a tracking checker’s results?

Read the report in two passes: first what is present, then what is actually firing. Presence tells you the stack, the tools on the shelf. Firing tells you which of them are live and sending data on the page you scanned. A tag can sit in the source and never fire, and a tag can fire twice, so the “is it firing, and how often” column is the one that catches real faults.

Three findings are worth acting on the moment you see them:

• A tag present but not firing. The script is on the page but sends no request. On your own site that often means GA4 is collecting no data, and every report built on it is running on empty.
• A tag firing more than once. A pixel or GA4 event that fires twice per page inflates conversions and pageviews, so the numbers read high and the optimisation built on them is wrong.
• Consent blocking more than expected. If tags are held back by a consent setup that denies by default and few visitors opt in, a large slice of EU and UK traffic never gets measured at all.

Why check what’s tracking on your own site?

Because presence is only half the question, and the accuracy half is where the money is. A checker confirms a Meta Pixel is on the page; it does not confirm the revenue that pixel reports is real. We once found a subscription box brand whose ad platform was claiming several times the revenue its own checkout confirmed, inflation the dashboards read as success. The tag was firing perfectly. What it reported was not true.

That gap between “the tag fires” and “the number is right” is what a tracking checker points you toward but cannot close on its own. A scan is the ten-second first look. When it surfaces something off, a double-firing pixel, consent holding back traffic, a conversion that stopped after a redesign, that is what talking to us is built to run down: whether the numbers you report actually match what happened in the business.

Start with a free scan to see what is installed and what is firing. Run Sonar on your own site first, then on the competitors you want to understand, and you will know both what your stack looks like and where it is quietly costing you.