Conversions API (CAPI)

A tracking pixel reports from the browser. The Conversions API reports from the advertiser's server (or their tracker's) straight to Meta. Meta's documentation says it accepts website, app, offline and messaging events and uses them for measurement and optimisation like other sources. TikTok's equivalent is the Events API, and Google offers comparable server-side conversion uploads.

For Social-to-search arbitrage, CAPI is how the money signal reaches the buying algorithm. The tracker learns what a visit earned from the feed, then sends Meta an event carrying a value, a currency and the visitor's click identifier (the fbc value built from the Click ID). Meta's bidding can then favour people who generate revenue, which is the basis of value-based bidding.

Three details from Meta's documentation shape the setup. If a pixel and the server both report an event, they are de-duplicated when event name and event ID match. Events can be sent with a timestamp up to seven days old, which leaves room for late feed revenue but not for month-end figures. And only data the user has consented to share should be sent, as GDPR and similar laws require.

Think of it like this

The pixel is a customer telling the supplier what they bought. CAPI is the shop sending the supplier its own sales ledger.

An example

Say a visitor arrives from Facebook, clicks a related search and then a feed ad. Hours later the feed reports about $0.80 for that visit. The tracker sends Meta a purchase-type event with value 0.80 USD and the stored click ID, and Meta credits the ad that sent the visitor.