Default cross-domain tracking in GA4?
I think I’ve found a new one, and I’m curious if anyone has seen something similar.
I work on a large site, with many separate subdomains, and also links to external domains.
What I inherited was a setup with each subdomain having its own property (along with a few rollup properties), which is fine - UA treated links between subdomains nicely, with no need for cross-domain tracking. I’ve had to set this up for a couple of properties with external connections (ecommerce, etc.), which is fine.
However, today I had a doozy. We use Optimizely for AB testing, and the tech responsible loaded a straight a href to another subdomain, but the link was completely unresponsive onClick.
He suspected our tag manager was the problem, so I debugged like mad - however, the tag manager code wasn’t even loading onClick.
After extensive debugging, I happened to notice in the Chrome dev tools network tab that there were calls being made to GA4 that weren’t being triggered by the tag manager, and realised that they were the default ‘exit link’ calls made from GA4, which we hadn’t disabled (though we possibly could have, given we also generate these from the tag manager - not GTM, BTW - but I don’t want to risk doxxing myself by giving too much detail, and I think it’s irrelevant).
When I looked closely at these calls, I noticed that the link URL had a gl= parameter included, which I recognised as being cross-domain tracking, and the link URL ended up being 254 chars long.
When I searched for an answer as to whether this could be a problem, G suggested it might be.
I have never set up cross-domain tracking in GA4 apart from the couple I mentioned earlier. When I went into the admin for this site, I discovered that (on top of the default exit-link tracking, which had never caused problems before) cross-domain tracking was set up in all of the properties associated with the site, with cross-domain tracking set up with various dev environments, etc., which is something nobody would do without very good reason.
I know I didn’t do this, nor any of my admin colleagues.
Is this cross-domain tracking (even of subdomains of the same parent domain) a new setting that Google has enabled by default to be ‘helpful’?
The moment I disabled all of this ‘functionality’ the links started working again, presumably because the link length was reduced.
I’d be interested if anybody’s seen this before, and also wanted to alert the community - if you find unresponsive links, this might be your issue, and it’s a nightmare to debug.