CAPI (Conversions API)
CAPI, Conversions-api, Tracking, Funnels
Server-side conversion tracking that sends events directly from your server to an ad platform, bypassing the browser pixel's blind spots.
CAPI - a Conversions API - is server-side conversion tracking. Instead of relying only on a browser pixel to report events like a lead or a purchase to an ad platform, your server sends the same events directly to the platform. Nothing in the browser can block it, and it can carry richer matching data (hashed email and phone), so match rates are higher.
It exists because the browser pixel has gone increasingly blind: ad blockers, browser tracking prevention, and consent rejections mean browser-only tracking now misses a substantial share of real conversions. Every lost event is a conversion the ad platform never learns from, which degrades targeting and inflates reported cost per lead. Server-side delivery recovers those events.
The recommended setup runs both the browser pixel and the server-side API, deduplicated by a shared event ID, so each conversion counts exactly once. Capturing ad-platform click IDs (fbclid, gclid, ttclid) and sending them with server events gives the strongest attribution match. The funnels guide covers pixel-versus-CAPI tracking, and the CAPI deep-dive details the failure modes.