Conversions API (CAPI)
Server-to-server event sending to ad platforms.
The Conversions API (CAPI on Meta, Events API on TikTok, Measurement Protocol on Google) is a server-side channel for sending events. Instead of the browser firing the event, your backend posts the event directly to the ad platform's API.
Why it matters: iOS 14.5+ App Tracking Transparency, ad blockers and cookie restrictions cause browser pixels to miss 25–40% of events. CAPI bypasses the browser entirely. Combining browser + server events with the same event_id deduplicates and recovers nearly all of the lost data.
Properly implemented CAPI typically lifts measured ROAS by 15–40% (the events were happening — you just weren't seeing them).