Why did domain_userid change?

We’re using the JS tracker 2.5.2. A user visited our site on 3/2. On 4/13, they visited again, from what looks like the same ip address (note that in between her visits, I turned off IP anonymization) and an identical useragent (now shown). The ipaddress shown below is fake, i just wanted to illustrate that I turned off anonymization in case that matters.

On her second visit, she was assigned a new domain_userid.

Am I misunderstanding the way the cookie works when I expect that domain_userid should be the same across these two visits? What are the potential reasons this could happen? I’m guessing if she deleted her cookies, that would do it. Are there other possible/likely causes?

Thanks in advance!

collector_tstamp user_ipaddress user_fingerprint domain_userid
2016-03-02 22:30:07 104.5.73.x 4174774485 568f3c60ec7f2453
2016-04-13 15:32:10 2415305789 1143aafe083380c6
2016-04-13 15:33:05 2415305789 1143aafe083380c6
2016-04-13 15:33:36 2415305789 1143aafe083380c6
2016-04-13 15:34:16 2415305789 1143aafe083380c6

That is indeed the most plausible explanation. I wouldn’t be concerned about this, as long as this doesn’t affect all (or a significant percentage) of visits.

You can use the other identifiers (the fingerprint, the IP address) to map different domain_userid onto each other. That’s what we refer to as the identity stitching process.

Hope this helps!