What is a tracking pixel?
How does a tracking pixel work?
You add the code to your pages. When a visitor does something you have set up, such as view a product, add to basket or buy, the code sends a message to the platform. The message names the event and may carry details, such as the order value.
The platform then matches that event to an ad the visitor saw or clicked. That match is where the platform's reported conversions come from.
Each platform has its own. The Meta Pixel is a common one in ecommerce. TikTok has a TikTok Pixel. "Pixel" is the general idea; those are products. A "tag" is a wider word for any piece of code managed in a tag manager.
Why do ecommerce brands use one?
Without it, the platform cannot see what happens after the click. It cannot report purchases and cannot learn which ads lead to them.
The weak point is the browser. A pixel runs there, so anything that limits it also limits what the platform sees. What it reports is what the pixel caught, not necessarily everything that happened. That is one reason to compare platform figures with your own orders.
What is the pixel's server-side companion?
Platforms offer a second route that sends events from your server instead. Meta's version is the Conversions API (CAPI). Meta describes it as a connection that sends data from an advertiser's server, website platform, app or CRM to Meta, covering website, app, business messaging and offline events1. Meta recommends running it alongside the Pixel, which it calls a redundant setup2. The server-side idea is covered in server-side tracking.
When the same event arrives by both routes, it has to be counted once. Meta's documentation says it treats events from the Pixel and the Conversions API as identical when the event name and event ID match2. See event deduplication. Without it, one purchase can look like two.
Easily confused with
Tracking pixel vs Conversions API
Sends events from a server, not the browser. Meta pitches it as a partner to the pixel, not a replacement.
Tracking pixel vs UTM parameters
Tags on a link that say where a visit came from. They tell analytics a source. A pixel reports actions to an ad platform.
Tracking pixel vs Cookie
A small file stored in the browser. A pixel may use one, but they are not the same thing.
A pixel is one of the first things to check in an ecommerce tracking audit. Which pixels exist and whether their numbers match your orders is a basic check.
FAQ
Is a pixel the same as a cookie?
No. A pixel is code that sends events to a platform. A cookie is a small file in the browser. A pixel may rely on cookies, but they are different things.
Do I need consent to run a pixel?
Pixels collect data about visitors, so consent and privacy rules can apply. Your counsel decides what applies to your site.
Sources
Let’s find what’s actually working.
Next step. Not sure your tracking counts each sale once? Start with our measurement and tracking audit.