Finally, I've been able to do what I want (sending the clientId value as a custom dimension to GUA) by setting up a js extension that looks like this: $waitUntil( function () { return (typeof ga !== 'undefined' && typeof ga.getAll === 'function'); }, function () { trackers = ga.getAll(); if(trackers.length) { utag.view({ client:trackers[0].get('clientId')}); }; }, 200, 2000); } What it does is: - waits until the GUA tracker is loaded - gets the clientId assigned to the visitor - calls utag.view to call the GUA tag where the client is mapped as a custom dimension. The drawback is that it generates duplicates the page views, as a page view is sent automatically when analytics.js library is loaded and I'm unable to skip it... Is it possible to set up the GUA tag to avoid the initial page view?
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