The Conversions API (CAPI for short) is Meta's interface for sending conversion events directly from a server to Meta. It complements the Meta Pixel, which runs in the browser, and makes your data far less dependent on ad blockers and browser restrictions.
How does the Conversions API work?
Instead of the visitor's browser reporting an event, a server sends an HTTP request to Meta's Graph API. Each event carries an event name (for example one of the Standard Events such as Lead or Purchase), a timestamp, the page URL and customer details like email or phone number. That personal data is hashed with SHA-256 before it is sent. Browser signals such as _fbp, _fbc or the fbclid can be included too, which improves matching.
The underlying principle is Server-Side Tracking: data moves from server to server instead of from the browser.
Why does the Conversions API matter?
Browser pixels can lose a noticeable share of events depending on your audience, for instance to ad blockers or Safari ITP. The Conversions API reduces that signal loss. Because it typically carries more customer data, it often raises your Event Match Quality as well, which helps Meta optimize delivery.
Deduplication is essential: when the pixel and CAPI send the same event, they need a shared event ID so Meta counts it only once.
Example
An online store tracks purchases with the pixel and also through the Conversions API. A customer with an ad blocker places an order. The pixel never reaches Meta, but the server event does, so the conversion still shows up in the campaign.
Conversions API with LeadSignal
Many Conversions API tutorials rely on a server-side GTM container you have to host yourself. LeadSignal skips all that: paste one script, connect your Meta account, and LeadSignal sends events through both the pixel and CAPI, deduplicated by event ID and enriched with hashed customer data from detected form fields. Walk through it step by step in How to set up the Meta Conversions API.