Hotjar fully supports cross-domain tracking for subdomains. This means that as long as the same Tracking Code is installed on each of the subdomains you want to track, Hotjar tracking will work as expected.
To set this up, install the same Tracking Code on all the domains you want to track under the same Site in Hotjar. You can get the Tracking Code from the Sites & Organizations page by clicking on the 'Tracking Code' button next to any Site you have set up.
Tracking domains separately
If you want to collect data for different subdomains separately you can also easily do this. Hotjar provides a unique Tracking Code for every Site you set up in your Organization. When you create new Sites, you will be provided with a unique Tracking Code per Site you need to install on each domain. You can read more in our Adding Sites to an Organization article.
Only users with admin access can create new Sites.