What is CAPI?
Also known as: Conversions API, Server-Side Tracking
Server-side Conversion APIs — the post-iOS 14.5 way to send conversion data directly from your server to ad platforms, bypassing browser-blocking.
The detailed definition
CAPI (Conversions API) is Meta's server-side tracking endpoint; equivalent products exist for Google (Enhanced Conversions), TikTok (Events API), Snap (CAPI), and X. The pattern is identical: your server sends conversion events directly to the ad platform via API, with hashed user identifiers (email, phone) where available for matching. This bypasses browser-side restrictions (iOS ATT, Safari ITP, ad blockers) and restores some of the attribution visibility lost since 2021. Server-side implementation is moderate engineering effort — most ecommerce platforms have first-party integrations or middleware (Stape, Aimerce, etc.) to streamline it. Not implementing CAPI in 2026 costs you 15–30% of attribution visibility on iOS-heavy accounts.
Related terms
Frequently asked about CAPI
›Do I need CAPI in 2026?
If meaningful spend goes to paid social and your audience skews iOS (most B2C does), yes. Not implementing CAPI costs 15–30% of attribution visibility post-iOS 14.5. Implementation is moderate engineering effort or zero-effort with middleware tools (Stape, Aimerce).
›What's the difference between CAPI and Pixel?
The Pixel runs in the browser; CAPI runs server-side. Pixel events get blocked by iOS ATT, Safari ITP, ad blockers, and tracking-prevention browsers. CAPI sends the same events from your server directly to the ad platform — invisible to browser-side blocks. Best practice is to run both (browser Pixel for any signal that survives + CAPI as the durable source of truth).
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