Unique Event ID by Up Blue

Custom GTM variable template that generates unique event IDs for deduplication between Meta Conversions API (CAPI) and GA4 browser-side events.

Installation

1. In Google Tag Manager, go to Templates > Search Gallery
2. Search for Unique Event ID by Up Blue
3. Click Add to workspace
4. Create a new variable using this template

How it works

The template generates a unique identifier by combining three components:

Component	Description	Persistence
Browser ID	Timestamp + random number	Per browser session
Page Load ID	Timestamp + random number	Per page load
Event ID	GTM's gtm.uniqueEventId from dataLayer	Per event

Output format

{browserId}_{pageLoadId}{eventId}

Example: 1647430000000555555_164743000000055555542

Usage

This variable is designed to be used as the Event ID parameter in both:

• Meta Pixel Tag (browser-side) — pass this variable as the Event ID
• Meta Conversion API Tag (server-side) — pass the same value via GA4 event parameter

Meta uses the Event ID to deduplicate events received from both the browser Pixel and the server-side Conversions API, ensuring each conversion is counted only once.

Typical setup

1. Create a variable from this template (e.g., named Unique Event ID)
2. In your Meta Pixel Tag, set the Event ID field to {{Unique Event ID}}
3. Pass the same value to GA4 as a custom parameter (e.g., event_id)
4. In your server-side Meta CAPI Tag, map event_id to the Event ID field

Configuration

This template requires no configuration — it works automatically out of the box.

License

Apache License 2.0 — see LICENSE for details.

Author

Built and maintained by Up Blue.