How to Check Which Tracking Pixels and Events a Website Fires

Whether you are auditing a client's site, checking a competitor's setup or confirming your own fix, the question is the same: which pixels are on this page, and which events do they actually send? Browser extensions give a quick answer. The Network tab gives the definitive one.

This guide covers both, from the method that works on any site to the tools that only work when you own the account.

Method 1: The DevTools Network tab (works everywhere)

A pixel is code that sends HTTP requests to an advertising or analytics platform. If no request leaves the browser, the platform received nothing, whatever an extension says. That makes the Network tab the most reliable check, and it works in Chrome, Edge, Firefox and Safari.

Set it up

1. Open DevTools (F12, or Cmd+Option+I on a Mac) and go to the Network tab.
2. Turn on Preserve log so requests survive page navigations and redirects. This matters for purchase and lead events that fire right before a redirect.
3. Optionally turn on Disable cache so scripts load fresh.
4. Reload the page, then perform the action you want to test.

Filter by platform

Type one of these into the filter box. They match the request URL, so partial strings work.

Platform	Filter	What to look for
Meta Pixel	facebook.com/tr	id (pixel ID), ev (event name), cd[value], cd[currency] and other cd[...] custom data
Google Analytics 4	collect	The measurement ID (G-...) and the event name in the request parameters
Google Ads	conversion	The conversion ID and label in the request URL
Google Tag Manager	gtm.js	The container ID (GTM-...) in the script URL
TikTok Pixel	analytics.tiktok.com	The library load plus event requests with the event name in the payload
Pinterest Tag	ct.pinterest	Query string parameters for the event and its data
Microsoft UET	bat.bing.com/action	Event requests; Microsoft documents a 204 response as expected
LinkedIn Insight Tag	linkedin or licdn	The snap.licdn.com script and requests to LinkedIn ad domains

Read each request

Click a request and check three tabs:

• Headers: the full URL and the status code. A 2xx status means the request was delivered. A failed request, or a status like (blocked:other) or (blocked:csp), means an extension or a Content Security Policy stopped it.
• Payload: query string parameters and, for POST requests, the request body. This is where you find event names, values, currencies, product IDs and event IDs.
• Initiator: which script sent the request. This is how you tell a hard-coded pixel from one fired by Google Tag Manager or a plugin, which is essential when hunting duplicates.

What to check in the requests

• How many pixel IDs? Two different Meta pixel IDs, or two GA4 measurement IDs, on one site is often unintentional.
• How many requests per action? One purchase should produce one Purchase event per pixel ID. Two requests means a duplicate.
• Are the parameters right? Value is a number, currency is a valid three-letter code, and product IDs match your catalog.
• Is there an event ID? If the site also sends server events, the browser event needs an ID that matches the server event so the platform can deduplicate.
• When does it fire? Requests sent before the visitor answers a consent banner tell you how consent is configured.

Method 2: Find what is installed in page source and console

Requests show what fires. To see what is installed but not firing, look at the code.

• In the Elements panel or the page source, search for fbq(, gtag(, GTM-, ttq, pintrk or uetq.
• In the Console, type dataLayer to see what the site has pushed to Google Tag Manager, in order.
• Watch the Console for errors from pixel scripts, such as a pixel object being undefined or a CSP violation.

Remember that code inside sandboxed iframes, such as Shopify custom pixels, does not appear in the main document. Their requests still appear in the Network tab. See Shopify pixels and Customer events for details.

Method 3: Each platform's own helper extension

Most ad platforms publish a free browser extension that decodes their own pixel's requests:

• Meta Pixel Helper for Chrome shows each Meta pixel ID on the page, the events it sent and any warnings.
• Google Tag Assistant starts a debug session from tagassistant.google.com and shows Google tags, their events and consent state.
• TikTok Pixel Helper for Chrome diagnoses TikTok pixel, event and parameter issues.
• Pinterest Tag Helper for Chrome lists events and their data. Pinterest notes that its event count accumulates as you navigate single-page sites.
• UET Tag Helper from Microsoft validates the UET tag one page at a time. Microsoft lists it for Edge and Chrome.

Each helper is accurate for its own platform and blind to the others. If you audit sites with several platforms, the Pixel Helper extension is another option, showing which pixels and events fire across platforms in one panel. Whatever extension you use, confirm anything surprising in the Network tab.

Method 4: GTM preview mode (your own containers)

If the site uses Google Tag Manager and you have access to the container, preview mode is the best way to understand why a tag did or did not fire.

1. In Tag Manager, click Preview and enter the site URL. Tag Assistant opens the site in a connected window.
2. On the left, each event in the timeline (such as Container Loaded, a click or a custom data layer event) is listed in order.
3. Select an event to see which tags fired and which did not, and why.
4. Use the Variables and Data Layer tabs to see the values each tag received.

Preview mode only shows tags inside GTM. Pixels hard-coded in the theme or loaded by plugins will not appear there, which is why you should pair it with the Network tab. If the session will not connect, see GTM preview mode not working.

Method 5: The platform's test tools (your own accounts)

Extensions and the Network tab prove a request was sent. Only the platform can tell you it was received and processed.

• Meta Events Manager > Test events shows browser and server events in real time. See how to use Meta's Test Events tool.
• GA4 DebugView shows events from debug sessions, including those started with Tag Assistant.
• TikTok Events Manager offers Test Events and diagnostics for your pixel.

Server events never appear in the browser, so these tools are also the only place to check a conversions API setup and its deduplication.

A quick audit routine

1. Open a clean browser profile with DevTools on the Network tab and Preserve log enabled.
2. Load the home page, accept consent, and note every pixel ID and its PageView.
3. View a product, add to cart, start checkout and complete a test purchase or lead.
4. For each step, confirm one event per pixel with the right parameters.
5. Repeat with consent declined and note what still fires.
6. Check the platform test tools for the same events, including server events.

FAQ

Can I see a competitor's events in their ad account?

No. You can see the requests their site sends from your own browser, which reveals the pixel IDs and events, but not what the platform recorded or how they use it.

The helper extension shows nothing, but the Network tab has requests. Who is right?

The Network tab. Extensions can miss pixels loaded in iframes, sandboxes or after single-page navigation. If requests leave the browser with a success status, the pixel fired.

Why do I see requests but no events in the platform?

Check the pixel ID in the request matches your account, that the status is 2xx, and whether the platform shows a processing delay. Test tools are faster than standard reports.

Do mobile browsers work the same way?

Yes, but inspecting them needs remote debugging from a desktop, such as Chrome remote debugging for Android or Safari's Web Inspector for iOS.