Thanks! Similar to how Plausible is doing. Each user gets a unique identifier which is based on `hash(domain+useragent+ip+salt)` (the salt is generated each day).
You'll never know any returning users after salt changes. This is the hole point with privacy first.
But you have options tho. Compared to other tools that is privacy first, you can actually pass your own user id. You can get this ID from where ever you want (db, cookie, localStorage. Its up to you whom implement it)
But I want to have a middle ground where privacy is important but you have the options to decide what path you take.
So maybe an obvious question but just to be clear, if you pass your own user ID you can track that particular user's flow across multiple sessions/days/etc?