The thing is it’s not exactly a fingerprint even though it works similarly when it’s active. The biggest difference is that it expires after 30 mins of inactivity and cannot be used to recognize returning visitors nor create user profiles.
- If I turn off Session ID, Piwik Pro will still stitch together Sessions (based on the Visitor ID cookie)
Yes, assuming that you didn’t change the default settings for that in the Site&app settings.
- Turning off the Session ID actually turns off FIngerprinting, not Session recognition (which happens on the server)?
Yes, session recognition is always done on the server.
Yes, _pk_ses.* cookie has nothing to do with the analytics session recognition that is done on the server side. The name is confusing, but it’s part of our Matomo’s legacy. This cookie is mainly used to update visits counter in the _pk_id.* cookie. This counter is used to generate some of the engagement reports, e.g. a table showing users grouped by no. of sessions or no. of sessions needed before the first order.