Meta pixel
The Meta pixel is Meta's JavaScript snippet that reports website events (PageView, Purchase, Lead) from the visitor's browser to Meta for measurement and optimization.
Formerly the Facebook pixel. It sets the _fbp cookie, captures the
fbclid click ID into _fbc, and reports events like PageView, AddToCart,
and Purchase that power ad measurement, audience building, and delivery
optimization. Your pixel ID lives in Meta Events Manager, under Data
sources.
#The pixel vs CAPI
The pixel is the browser half of a two-transport system, and it no longer
works alone: ad blockers, Safari's cookie caps, ATT, and consent banners
all erode it. Meta's answer is redundancy: the Conversions API sends the
same events server-side, and Events Manager deduplicates the two streams by
shared event_id. Pixel alone undercounts; both without dedup
double-counts.
What the pixel still sees today, and where to find your ID, is covered in The Meta Pixel: what it is, what it sees, where to find your ID. The choice between transports is Conversions API vs the Meta Pixel.
Related terms
Conversions API (CAPI)
The Conversions API is Meta's server-to-server channel for conversion events: a second delivery route for the same events the pixel sends from the browser.
Tracking pixel
A tracking pixel is a tiny image or script that fires an HTTP request on a pageview or event, carrying the URL, referrer, timestamp, and identifiers to a collection server.