Event Deduplication for Meta: How to Avoid Double-Counting Conversions
When you run both browser pixel and server CAPI, deduplication prevents Meta from counting the same conversion twice. Here is how to implement it correctly.
Marcus Tillman
Senior Tracking Engineer · 2024-10-10
Event deduplication is one of the most commonly misunderstood aspects of running browser + server tracking simultaneously. Get it wrong and your conversion numbers will be inflated.
How Deduplication Works
Meta deduplicates events using two signals: 1. **event_id** — a unique string you generate and send with both browser and server events 2. **fbclid** — the Facebook click ID from the URL
Meta checks if two events share the same event_id (and optionally eventSourceUrl + fbc). If they do, it counts them as one conversion.
Generating Event IDs
The simplest approach: generate a UUID when the page loads and use it for all events fired on that page. Pass the same UUID in both the pixel event and the CAPI event.