Universal Pixel DebuggerWhat tracking pixels actually send: a study of 38 websites
Updated 2026-09-28
On 26 September 2026 we opened 38 websites in Chrome with Universal Pixel Debugger and read every tracking request each one sent on its first page. The short version: a typical page talks to eight ad and analytics networks at once, most sites send some events to several accounts of the same network, and about one event in five carries no event name at all.
Everything below counts what the browser sent. It does not show what any network accepted, attributed or reported, and it says nothing about server-side tracking, which never passes through the browser.
How we checked
- Sites: 38 websites chosen so that every network the extension supports appears somewhere: 28 online stores and 10 software, media and service sites, in Europe, the Americas and Asia. No site is named here.
- What we did: opened one page per site (the home page or a product page), waited about 16 seconds, and read the capture. We did not answer consent banners, click anything or buy anything.
- How events were read: with the extension's own decoders, so event names, values and currencies are exactly as sent, and the checks below are the same ones the extension shows.
- Result: 34 of the 38 sites sent at least one decoded event on that page, 692 events in total. The other four sent none before any interaction; we did not investigate why (a consent banner waiting for an answer is one possible reason).
A typical page talks to eight networks
The median site sent events to 8 networks on its first page, and the busiest sent to 12. The median page produced about 20 events before the visitor did anything.
| Network | Sites sending events |
|---|---|
| Google Analytics 4 | 28 of 34 (82%) |
| Google Ads | 27 of 34 (79%) |
| Meta Pixel | 27 of 34 (79%) |
| Microsoft Advertising UET | 23 of 34 (68%) |
| TikTok Pixel | 16 of 34 (47%) |
| Pinterest Tag | 11 of 34 (32%) |
| Google Floodlight | 10 of 34 (29%) |
| Reddit Pixel | 9 of 34 (26%) |
| Criteo | 8 of 34 (24%) |
| LinkedIn Insight Tag | 7 of 34 (21%) |
Among the 25 online stores that sent events, Google Ads, Meta and GA4 were each present on 80%, and TikTok on 56%.
Most sites send one event to several accounts
21 of 34 sites (62%) sent at least one event to more than one account of the same network: several Meta pixels, several Google Ads accounts or several GA4 properties. The most common case was Google Ads (9 sites), followed by Meta and GA4 (4 sites each). One event went to as many as 8 destinations.
That is often deliberate, for example an agency account next to the brand's own, but each destination counts the event separately. It also explains a lot of "duplicate" worries: the same Purchase sent to two pixels is two destinations, not a duplicate. Our guide on duplicate purchase events shows how to tell the difference.
On one site, two Google Ads accounts received the same event with different data: one got a currency and the other did not, and the product IDs differed in case. When destinations disagree like that, the account with the missing field reports the event without it.
Google Ads sends each hit twice, in two formats
Of the 27 sites sending Google Ads events, 25 sent the same hit both as a CCM request and as a view-through request. That is how the Google tag works, not a double count, but it doubles the number of Google Ads requests you see in the browser. Why one Google Ads hit becomes several requests explains each format.
One event in five has no event name
130 of the 692 events (19%), on 29 of 34 sites, carried no event name. They are page hits and base-pixel requests that identify themselves by their format rather than by a name, such as a Google Ads page hit or a pixel's first request. The extension labels them by type in grey so they can't be mistaken for a sent name, and you can hide them from the list.
Values without a currency
4 of 34 sites (12%) sent a value with no currency on the first page; in all four cases it was Google Ads. A value without a currency can't be converted or compared reliably. The same problem in GA4 purchases has its own guide: GA4 purchase without currency.
Other findings
- Consent commands: 11 of 34 sites (32%) sent a Google consent-mode command we could see in the page. That shows the command, not the effective consent state, and it is not a compliance check.
- Requests with no decoded event: 3 sites sent a request to a supported network that carried no recognizable event.
- Failed requests: 1 site had a tracking request fail in the browser.
- First-party Google tag: 1 site sent its Google requests through its own domain (a tag gateway) instead of Google's hosts.
What this means for your own site
- Expect more networks and more requests than your tag manager suggests. Apps and platform integrations can add their own.
- Check where each event goes, not just whether it fired. An extra or outdated account quietly receives your data.
- Check that every value travels with its currency, on every destination.
- When two networks report different revenue, compare what each one received first: why Meta and GA4 report different revenue.
Limits
Thirty-eight sites is a small, hand-picked sample, chosen for network coverage rather than to represent the web. We looked at one page per site, without consent and without purchases, so checkout events and anything that waits for consent are not counted. Browser requests are not what networks report: they may reject, deduplicate or attribute events differently, and server-side events are invisible here. We plan to repeat the check and update these numbers.