Probably UUIDs based on fingerprinting the browser/machine. With enough js there’s usually enough to qualify a person’s activity as unique even with minor changes regarding updates or whatever. You can mitigate it by changing user agent strings or disabling some/all js or site permissions, but they can also block you from using the service for doing so, so ¯\_(ツ)_/¯.
Not sure that existed, but how would it work? There were no accounts and IPs are ephemeral.
Probably UUIDs based on fingerprinting the browser/machine. With enough js there’s usually enough to qualify a person’s activity as unique even with minor changes regarding updates or whatever. You can mitigate it by changing user agent strings or disabling some/all js or site permissions, but they can also block you from using the service for doing so, so ¯\_(ツ)_/¯.