Custom Event named as an Automatic Event will duplicate events in GA4

Some days ago I found a question on Reddit asking what happens when Custom Event and GTM GA4 Event have the same event_name? I wanted to be 100% sure about the answer so I decided to do a pretty simple test I will show in the next lines.

The most complete guide I’ve found about duplicate events in Google Analytics 4 is of course something by Julius: https://www.analyticsmania.com/post/duplicate-events-in-google-analytics-4-and-how-to-fix-them/.

Unfortunately, that wasn’t enough for what I wanted to prove, so I hope I can help someone sharing how I tested it, precisely tackling the question.

How I set GTM to duplicate an automatic event

First things first, I set a GA4 event tag on Google Tag Manager replicating an automatic event. I’ve chosen the GA4 event page_view, but it could have been anything else.

Triggers were exactly the same to be sure they fired at the same time (see snapshot below).

The Google Tag - sending a page_view - and the parallel custom GA4 page_view event I set

The GA4 event tag was set by adding just a custom parameter to let me easily recognize what I was looking at in the DebugView.

The GA4 event tag is set with a custom parameter foo with value bar

Results: Will both automatic and custom GA4 events fire?

I haven’t published my new version of the GTM container but simply used the Google Tag Assistant to test the results in the GA4 DebugView.

The results were straightforward. Both the automatic page_view and the custom page_view were fired. The first page_view event was the automatic one while the second contained the custom parameter foo.

page_view automatic event automatically created by GA4

page_view custom event with custom parameter foo

Here we go, a complete test to successfully prove what happens when automatic events get duplicated with custom ones. There’s no deduplication on Google’s side, so look out!