Cross Domain tracking on two different properties in GA?

Question

I've been researching how to add cross-domain tracking for two different domain names. We currently have two different properties for two different sites, Site A and Site B. Unfortunately we have a shared form system which lives on one subdomain (subdomain.sitea.com), but we share this form system across both websites.

The problem is, we can't follow the user's journey on Site B as, as soon as the user goes to Site's A form system it stops tracking the user's journey. It would also be nice to know if any visitors from Site A leave, but visit Site B at another time - basically giving us an idea of shared visitors.

I've been reading a lot about cross-domain tracking with GA, but it sounds like it only works if both sites are on the same property in Google Analytics. I don't want to lose any of the historic data relating to either sites either.

Is it possible to create another property and load the new GA tag on both sites, effectively loading two GA tags on both domains? Or is there another way of tackling this problem without losing our Google Analytics data?

Answer 1

Sharing information between two Analytics properties? No. Analytics doesn't work like that. With very few exceptions you can't add data to an Analytics property except through various user tracking methods.

There are ways you could add extra information to traffic between sites, using tagging of URLs or to add exit events for those users. But this wouldn't give you the full picture of what those users do once they have switched sites or switched back. They'd all be lumped together as referral traffic, so you wouldn't be able to distinguish the actual originating traffic source.

So, unfortunately, you're left with your second option; a new Analytics property connected to both sites.

Yes, this is perfectly possible. Yes, it's OK to load two different Analytics tracking elements on the same page. It's generally best to replicate the same tracking method twice. For instance, if you have the UA snippet, just use it again for the new property.

This might be complicated if your sites use something like WordPress, as plugins tend to not permit multiple Analytics properties. If so, you might consider switching to Google Tag Manager. As with one GTM container you can send pageview or event data to multiple Analytics properties.

You won't lose your existing Analytics data, that will all still be there, and you can continue to feed data into those properties. But cross-domain tracking is only possible using a combined property for both sites.