CAPI stands for Conversions API, a way to send conversion events to ad platforms directly from your server instead of relying only on a browser pixel. As browser tracking becomes less reliable, CAPI has moved from 'nice to have' to essential for serious advertisers.
The problem CAPI solves
Browser pixels depend on cookies, JavaScript, and the browser cooperating. Increasingly, they don't. iOS privacy changes, ad blockers, cookie loss, and stricter browser policies all cause conversions to go unrecorded.
When conversions go missing, platforms optimise on incomplete data, and your reports understate real performance.
How CAPI works
Instead of relying on the browser, your server sends the conversion event straight to the platform. Meta calls it CAPI, TikTok calls it the Events API, and Snapchat has its own Conversions API. The concept is the same: a more reliable, server-side signal that isn't blocked by the browser.
CAPI done wrong can make things worse
Here's the catch: if you send both a browser event and a server event for the same conversion without proper event IDs and deduplication, you double-count. Now your numbers are inflated instead of accurate.
A correct CAPI implementation requires:
- Consistent event IDs shared between the pixel and the server event
- Proper deduplication so one conversion is counted once
- Strong parameter matching to maximise event match quality
- Validation that events actually arrive and match as intended
The bottom line
CAPI is one of the most effective ways to recover lost signal and improve optimisation, but it has to be implemented and validated properly. A botched setup trades one problem (missing data) for another (duplicated data).
Related reading: our services and the Measurement Health Audit.
Think this might be happening in your account?
A Measurement Health Audit traces every conversion end to end and tells you exactly what's duplicated, missing, misfiring, or misaligned.