Seeing user info cross domain

General questions
1

We have a family of 4 websites Membership Site, Sales Page Site, Content Site A and content Site B. All of them have matomo. One of them is our Wordpress membership site. On the membership site I am using Matamo to see analytics by userid. These membership users also bounce between the content sites and the sales page site. Is there any way to see userid information of the non-membership site clicks. Example: bob@google.com visits content site A, logs into membership site, then goes to content site A or B. In the analytics for the member site site I’ll see his user info and history . But can I also use that user info to see his activity on content site A and B? That way I can get a full picture of clicks as users go between the 4 sites (Note: I know we won’t get userid information from anonymous users)

2

Hi

Assuming that the 4 are completely different domains and not subdomains of a parent domain, the only option I can think of is cookies, but with some caveats. Most web apps mandate the use of cookies, so this is reliable to a large extent.

  1. 3rd party cookies: ugggh… not recommended as they can be spoofed, and many browsers and users may block these
  2. use cookies, but with every server request done by the front end, synchronize the cookies info on your various backends, so that you validate the cookie and take action based on the cookie’s signature, etc., possibly using JWT tokens or something similar

Allow me to elaborate

  1. User visits ABC.com and doesn’t login. Whenever there is a server interaction (which you may also trigger by a javascript from the front end, for example), the user has cookie value of 1111111.
  2. The backend on ABC.com validates if the cookie was set using its own JWT token mechanism and stores that somewhere where DEF.com and XYZ.com can also have access to that info (on a commonly used database, for example)
  3. Same process when the user logs in to any one of those sites
  4. Some disadvantages I can think of is a lag between the different sites, sessions going out of synch if user logs in on multiple tabs/windows, etc., but these can be addressed

Am i making sense?

Thanks