Why is it not possible to anonymise User ID?

I chose Matomo for user privacy reasons but when User ID’s can only be pseudonymised I’m having second thoughts, even Google lets you disable User ID’s. Why don’t we have more control over this option?


User ID is a feature where you intentionally add personal data to the tracked data by e.g. calling

_paq.push(['setUserId', 'tom@example.com']);
// or 
_paq.push(['setUserId', 'steve']);

So if you don’t want this personal data to land on your Matomo server, the solution is simply to not set the userid. Then Matomo will use the normal anonymized ids.

1 Like

Thank you for that response Lukas! I was unaware of this and feel relief after knowing this, I will read up on User ID to get a better understanding.

Can I ask you this as well: If I have disabled cookies and anonymise IP-adresses, is it still possible to track unique visitors? It would be valuable to have this statistic, but I understand if I cant get the best of both worlds (I don’t want to store any personal information, or data that can identify a person).


It is explained in this FAQ: How does Piwik detect unique and returning visitors? (with User ID, Visitor ID from cookie and/or fingerprint) FAQ - Analytics Platform - Matomo

Basically if you disable cookies, Matomo tries to detect unique visitors by “operating system, browser, browser plugins, IP address and browser language”.