Across (sub)domains in piwik pro tag

I see there are 2 options available for across-domain and subdomain checking.

If I have 3 sites,, and In which condition I need to turn on across-domain and subdomain checking in piwik pro tag?

Hi. Their first two are not even subdomains, so everything should work out of the box without any adjustments. Just make sure that the same installation code was used to add Piwik PRO. As for the 3rd domain, you would have to set up cross-domain tracking.

Sorry for my mistake, it should be and

For 3rd domain, can I just simply turn on the cross-domain tracking option without editing anything in Piwik pro tag?

Then you have to set up cross-subdomain tracking as well. So, for this case:

  • you use same installation code
  • you set cookie domain to * in the Piwik PRO tag in tag manager for both sites

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