Step 6. Configure deduplication

Facebook recommends sending events using both Facebook Pixel and Conversion API. To prevent overreporting, you need to implement deduplication. Facebook will treat events as identical if they have the same event name and event ID and were sent within 30 minutes. So, the critical element in Facebook deduplication is sending the same event ID for identical events in web GTM and server GTM. To simplify this process, we created a unique event ID variable for web GTM. 

1. Add Unique Event ID variable to your web container.

2. Add event_id variable to each Facebook pixel tags inside the web GTM container. 

3. Add a unique event ID to each GA4 or Data tag (depends on what method you choose to use for sending data from web to server GTM)  inside the web GTM container.  

• If you use GA4, add event_id parameter to Google tag configuration settings. 

• If you use Data Tag, add the event_id to every Data tag in the web container.

4. Create a new event_id variable in sGTM, follow these steps:

 - Go to your sGTM container.

 - Create a new variable.

 - Select the type "event data."

 - Add a key path event_id.

The key path should match the name of the variable you use in web GTM. This step is the same whether you send a unique event ID using GA4 or a Data tag.