impact of different GA scripts[ Edited ]
September 2016 - last edited September 2016
What's the impact of using multiple and different versions of trackers on the same domain and whats the best way to achieve this?
domain-a.com -> ga.js UA-11111111-1
domain-b.com -> ga.js UA-22222222-2
1) add 1 GTM account with 1 Universal Analytics ID to track both domains in 1 property.
2) Keep the 2 seperate legacy scripts as well on the page.
Re: impact of different GA scripts
I'm confused as you said same domain then in #1 of your requirements you have "...track both domains". Dual tracking can be done but requires customized versions of the code where the second tracker gets named. There are some limitations to this as only one cookie set is used.
If you are using GTM, it's much easier as you can just deploy the same trackers in two tags and GTM will take care of the rest.
If your requirements are truly that, then you can do as planned -- as long as the new UA tag is not using the same account and property --and keep the legacy trackers on (make sure that one is named otherwise your data is not reliable) the page and then deploy universal via GTM.
That said, the strategy behind this tracking should be considered as whether or not it's needed or relevant.