Follow the steps below to create and pass the client ID custom parameter (with user scope) along with the event named ‘get_user_data’ to our GA4 property.

Step-1: Login to your Google Tag Manager account and then click on the ‘Templates‘ link:

Step-2: Click on the ‘Search Gallery‘ button under the ‘Tag Templates’ section:

Step-3: Click on the magnifying glass to display a search box:

Step-4: Type ‘GTAG GET API‘ in the search box and then click on the first search result:

Step-5: Click on the ‘Add to workspace‘ button:

Step-6: Click on the ‘Add‘ button:

You should now see the new tag template listed under the ‘Tag Templates‘ section:

Now, we are going to create a new tag based on this tag template.

Step-7: Click on the ‘Tags‘ link and then click on the ‘New‘ button to create a new tag:

Step-8: Name the new tag ‘Gtag get api‘:

Step-9: Click on the ‘choose a tag type’ button:

Step-10: Scroll down and then click on the custom template ‘GTAG GET API‘:

Step-11: Enter the measurement ID of your GA4 property and then click on the ‘Save‘ button:

Step-12: Click on the ‘Save Tag‘ button, as your tag will not have any firing trigger:

Now, we need to edit the GA4 configuration tag (the Google tag we used to install and enable the GA4 tracking) and add the tag ‘Gtag get API‘ in a tag sequence.

Step-13: Find and edit your Google tag and then click on the ‘Advanced Settings‘ link:

Step-14: Click on ‘Tag Sequencing‘:

Step-15: Click on the checkbox ‘Fire a tag after Google Tag – All Pages fires‘:

Step-16: Click on the ‘Select tag‘ drop-down menu:

Step-17: Click on the ‘Gtag get api‘ tag:

Step-18: Click on the ‘Save‘ button to save your tag:

Step-19: Click on the ‘Triggers‘ link and then click on the ‘New‘ button to create a new trigger.

Step-20: Name the new trigger ‘gtagApiGet‘ and then choose the trigger type to ‘Custom Event‘:

Step-21: Type ‘gtagApiGet‘ in the ‘Event Name’ text box and then click on the ‘Save‘ button:

Step-22: Click on the ‘Variables‘ link and then click on the ‘New‘ button under the ‘User-Defined Variables‘ section:

Step-23: Name the new variable ‘Return Client ID‘ and then set the variable type to ‘Data Layer Variable‘:

Step-24: Type ‘gtagApiResult.client_id‘ in the ‘Data Layer Variable Name’ text box and then click on the ‘Save‘ button:

Step-25: Click on the ‘Tags‘ link and then click on the ‘New‘ button to create a new tag:

Step-26: Name the new tag ‘Send client id to GA4 test property‘ (or whatever best works for you) and then select ‘Google Analytics: GA4 Event‘ as the tag type:

Step-27: Enter your measurement ID:

Step-28: Type ‘get_user_data‘ in the ‘Event Name‘ text box:

Step-29: Click on the ‘User Properties‘ drop-down menu:

Step-30: Click on the ‘Add Row‘ button:

Step-31: Type ‘client_id_custom‘ in the ‘Property Name‘ text box and ‘{{Return Client ID}}.‘ in the ‘Value‘ text box:

Note: Make sure that you add the dot . after the {{Return Client ID}} variable to force GA4 to treat the value of this variable as a string and not a number.

Step-32: Click on the ‘Choose a trigger’ button:

Step-33: Click on ‘gtagApiGet‘ trigger:

Step-34: Click on the ‘Save‘ button to save your new tag:

Step-35: Click on the ‘Preview‘ button to preview your GTM container:

You should now be automatically redirected to a new tab in your web browser. 

Step-36: Enter your website address and then click on the ‘Connect‘ button:

You should now be automatically redirected to a new tab in your web browser which shows your website content. 

Step-37: Navigate back to your Tag Assistant window and then click on the ‘Continue‘ button:

You should now be able to see the ‘gtagApiGet’ event listed in the event list and the tags ‘Send client id to GA4 test property‘ & ‘Gtag get api‘ listed under the ‘Tags fired’ section:

Step-38: Navigate to the ‘DebugView‘ report of your GA4 property:

Step-39: Find and click on the user property named ‘client_id_custom= ……‘:

Step-40: Find and click on the user property named ‘client_id_custom‘:

You should now be able to see the captured client ID:

Step-41: Navigate back to Google tag assistant window and then close it by clicking on the cross button at the top left-hand side:

Step-42: Click on the ‘Stop debugging’ button:

Step-43: Navigate back to your GTM account and then click on the ‘Submit‘ button to publish your container:

Step-44: Enter your container version name and then click on the ‘Publish‘ button:

That’s how you can create and pass a user scope custom parameter along with an event.