Conversion API Implementation

CAPI lets advertisers send conversion data server-to-server, bypassing browser-pixel limitations. This module covers Meta CAPI, Google EC, and the patterns that produce 10 - 50% more measured conversions.

What you will learn

What Conversion API is and why every paid-media program needs it
Meta Conversions API: the canonical implementation
Google Enhanced Conversions and Conversion API
TikTok Events API, LinkedIn CAPI, Snap CAPI
The event-quality match-quality score
Customer data and hashed identifiers
Event deduplication: pixel + API both
Click identifier (CLID/FBCLID/GCLID) handling
Common CAPI mistakes
CAPI for offline conversions
Measurement and validation

1. What CAPI does

Conversion API (CAPI) lets advertisers send conversion data directly from server to ad platform, bypassing the browser-pixel limitations of client-side tracking. Result: 10 - 50% more conversions reported, higher match rates, better campaign optimization.

2. Meta Conversions API

The canonical implementation. Server sends events to Meta's API endpoint with: event name, event time, user_data (hashed identifiers), custom_data (value, currency, content_ids), action_source, event_id (for deduplication).

3. Google's versions

Enhanced Conversions for web: Adds hashed user data to existing client-side conversions.
Enhanced Conversions for leads: Server-to-server for offline conversions.
Conversion Linker: Solves cross-domain attribution in privacy-restricted browsers.

4. Other platforms

TikTok Events API.
LinkedIn CAPI.
Snap CAPI.
Pinterest CAPI.
Reddit CAPI.
All similar conceptually; specifics differ.

5. Match quality

Meta's Event Match Quality score (0 - 10) reflects how well your events match Meta's identity graph. Higher match quality = better attribution and optimization. Improve by sending: email (hashed), phone (hashed), first/last name (hashed), city, state, zip, country, IP, user agent, click identifiers.

6. Hashed identifiers

SHA-256(normalized email) where normalized = trim + lowercase

Same hashing applies to phone (E.164 format), names (lowercase, no punctuation), and other identifiers.

7. Deduplication

Most implementations send the same event via pixel AND CAPI for redundancy. To prevent double-counting:

Use the same event_id in both pixel and CAPI.
Send within the deduplication window (typically 48 - 168 hours).
Use consistent event names.

8. Click identifier handling

FBCLID (Meta click identifier): capture from URL parameter, store in first-party cookie, send with CAPI events for 7+ days.
GCLID (Google click identifier): same pattern.
TTCLID, LICLID, etc.: each platform has its own.

9. Common mistakes

Not hashing user data correctly. Missing event_id for deduplication. Sending raw PII. Failing to forward click identifiers. Not implementing for all key conversion events. Setting up but not monitoring.

10. Offline conversions

CAPI is the bridge from CRM / EHR / call-center conversions to digital ad platforms. Send conversion data with the original click identifier or hashed customer match to attribute.

11. Validation

Meta Test Events tool.
Server-side container preview mode.
Vendor diagnostics dashboards.
Compare CAPI-only vs pixel-only to confirm deduplication.
Monitor match quality over time.

How to use this module: The Meta CAPI structure (Section 2), the deduplication pattern (Section 7), and the validation checklist (Section 11) are the planning artifacts.

Sources & further reading

Part of the GTM Server-Side series · RGM Training