Tracking pixel
A tracking pixel is a JavaScript snippet or a 1×1 px image loaded on a page to signal a visit or action to a third-party platform (Meta Pixel, TikTok Pixel, LinkedIn Insight Tag) for retargeting or advertising measurement purposes.
In practice
The Meta Pixel sends browser events (PageView, AddToCart, Purchase) to Meta to optimize campaigns and build retargeting audiences. Since iOS 14.5, ATT consent has reduced pixel coverage on mobile by 40 to 60%. The replacement is Meta Conversions API (CAPI) — server-side, less affected by browser restrictions — used alongside the pixel for event deduplication.