Tracking & optimisation · also called pixel, Meta Pixel, TikTok Pixel, conversion tag
Tracking pixel
A tracking pixel is a small piece of code on a web page that tells an ad platform, through the visitor's browser, that a page view or action took place.
The name comes from the original trick: an invisible one-pixel image whose loading told a server that a page had been opened. Today a pixel is a JavaScript snippet from Meta, TikTok, Google or a native network. It runs in the visitor's browser, reads the platform's identifiers and reports events such as "page viewed" or a custom conversion.
Arbitrageurs place the traffic source's pixel on their landers so the platform can see what its clicks did. On a page with related search terms, the pixel might fire when the page loads and again when a term is clicked.
Pixels have two weaknesses in this business. They are browser-side, so ad blockers, tracking prevention and consent choices stop a share of events from arriving (see consent management). And the event that matters most, the paid ad click, happens on a results page and is reported later by the feed, where a browser pixel cannot see it. That is why operators pair the pixel with server-side reporting through a Conversions API, using a shared event ID so the same event is not counted twice.
Think of it like this
It is the bell above a shop door. It rings when someone walks in, unless they came through a door with no bell fitted.
Related terms
Conversions API (CAPI)
The Conversions API is Meta's server-to-server interface for sending conversion events and their values to Meta directly, without relying on the visitor's browser.
Postback (server-to-server tracking)
A postback is a message sent directly from one company's server to another's to report that a tracked click produced a conversion or revenue.
Click ID
A click ID is a unique code an ad platform or tracker attaches to each ad click so that later events can be matched back to that exact click.
Attribution
Attribution is the process of deciding which ad, click or traffic source gets the credit for a conversion or a piece of revenue.
Consent management (CMP)
Consent management is the process, usually a cookie banner run by a consent management platform, of asking visitors for permission before using their data for ads.
Tracker (campaign tracking platform)
A tracker is software that records every click an arbitrageur buys, matches it to the revenue it later earns, and reports profit by campaign, ad and keyword.
Sources: Meta for Developers: Deduplicate Pixel and server events, TikTok Business Help Center: About Events API