Conversions API (CAPI)
The Conversions API is Meta's interface for sending conversion events from your server to Meta instead of relying only on the browser pixel. A server event carries the same payload a pixel would send — event name, timestamp, user identifiers — but it is delivered from your infrastructure, so ad blockers, browser tracking prevention and lost cookies cannot silently drop it.
What CAPI sends
A CAPI event is a JSON payload with an event_name, an event_time, an
action_source (website, app, …) and optional user data such as email,
phone or client IP — hashed before leaving your server. Events arrive at the
dataset level: the same dataset the pixel belongs to, which is why a pixel ID
and an access token are the two credentials every integration asks for.
How CAPI and the pixel work together
The common setup sends each conversion through both channels: the pixel for
browser coverage, CAPI for everything the browser loses. When both events
share a stable event_id (and event name), Meta counts the pair once. See
event_id and deduplication for the
mechanics.