Questions about cookies and domain_userid


We setup snowplow with success and can now actively track customers based on their domain_userid.
How this domain_userid is built thought? How can I guarantee that it will be different from a user to another?

Thanks, Guillaume

Hi @gtd,

The domain user ID (domain_userid in is a UUID, which the Javascript tracker generates and writes to a cookie for future visits. Because it’s a UUID, it should be impossible in practice for 2 different visitors to get assigned to the same domain_userid. The domain_userid does suffer from the traditional limitations associated with cookie storage, but, all things considered, we still recommend it as the main identifier for visitors that are not logged in.

For more information on our Javascript tracker, I recommend checking the documentation:

I hope this helps. Let me know if you have any follow-up questions.


Hi @christophe,

Thanks a lot, this is much clearer for me now.
I will also check the documentation before asking if I have more questions.