Event Deduplication in Google Tag Manager

Event deduplication in Google Tag Manager (GTM) ensures that when events are tracked both through the web container and the server container, duplicates are prevented. This functionality is crucial for accurate data collection and analysis, particularly when integrating platforms like Meta that distinguish between client-side and server-side events.

What is Event Deduplication?

Event deduplication in GTM involves the removal of duplicate events to prevent skewed data. This is particularly important when the same user interactions are tracked in multiple ways—such as both through a browser (client-side) and from a server (server-side). Deduplication ensures that each unique event is counted only once, regardless of how many times it is sent to GTM.

Example with Meta

Meta (formerly Facebook) differentiates between events triggered by the pixel (client-side) and those from the conversion API (server-side). To manage duplicates, Meta uses a "Unique Event ID" for each event, allowing the system to identify and disregard repeated events across different tracking environments.

Implementing Event Deduplication:

  1. Assign a Unique Event ID: Each event sent from both client-side and server-side must have a unique identifier.
  2. Configure GTM Containers: Set up event deduplication in both the web and server GTM containers to utilize the Unique Event ID.
  3. Validate Setup: Ensure that events are properly deduplicated by testing the tracking of events to see that duplicates are effectively filtered out.

Platform-Specific Deduplication

While some platforms like Google's own products handle deduplication automatically, others do not and require manual setup. It is essential to check whether a platform requires manual event deduplication and configure it accordingly. We consistently mention in our configuration blogs whether or not to use deduplication based on the platform being integrated.


By effectively managing duplicate events, you can ensure more accurate reporting and insights, which are essential for optimizing digital marketing strategies.