I am creating a "privacy-focused" analytics tool[0], that actually provides useful stats.
The privacy part, compared to other tools, comes from the fact that it's self-hosted, so no data is shared with 3rd parties, which is the best way to achieve data privacy.
You can detect returning visitors in various way, an option in userTrack is to store the hash of IP + user-agent string of the visitor. It is not 100% accurate and if the visitor updates his browser or his IP changes it will be considered to be a new user.
If the user is logged-in, you can tag each session with his username or user ID.
Also keep in mind that fully persistent identities rarely exist (unless the user is logged-in), as the cookies can be cleared at any point or simply be blocked/reset by the browser on each visit.
PS: I do agree that many privacy-focused tools are also not really private, because they still are a 3rd-party aggregating data across the web.
The privacy part, compared to other tools, comes from the fact that it's self-hosted, so no data is shared with 3rd parties, which is the best way to achieve data privacy. You can detect returning visitors in various way, an option in userTrack is to store the hash of IP + user-agent string of the visitor. It is not 100% accurate and if the visitor updates his browser or his IP changes it will be considered to be a new user. If the user is logged-in, you can tag each session with his username or user ID.
Also keep in mind that fully persistent identities rarely exist (unless the user is logged-in), as the cookies can be cleared at any point or simply be blocked/reset by the browser on each visit.
PS: I do agree that many privacy-focused tools are also not really private, because they still are a 3rd-party aggregating data across the web.
[0]: https://www.usertrack.net/