Pixel

A tracking pixel is a small, invisible piece of code embedded on a website. It is used to capture user interactions and send the data to external services — usually for tracking, conversion measurement or personalised advertising.

A well-known example is the Facebook Pixel (now generally known as the Meta Pixel), which sends data to Facebook/Meta in order to:

• conversions from Facebook Ads,
• build audiences for remarketing campaigns,
• and analyse user behaviour across multiple pages.

Technically, a pixel works by loading an invisible 1×1 image. At the same time, information such as the page URL, user ID or eventdata is sent to the provider.

Because pixels are usually implemented client-side , they are increasingly affected by tracking blockers, consent-management tools and data-protection rules. An alternative is server-side tracking, where pixel requests are recreated and managed on the server.