What a coincidence... I was just a few seconds ago, before taking a break to read HackerNews, investigating an issue with a Chromium blocker (https://github.com/gorhill/httpswitchboard/issues/79#), and was puzzled finding that the `pref` cookie of `.google.ca` changed every single time the tab of the page lost focus. Even went to Google privacy page to understand what this cookie did, with nothing in their statement that could explain this. Now this?
No. I prefer the scientific approach. At this point, I just reported what I observed. Maybe somebody will come up with a sensible hypothesis as to why a value changes so often. Google could just come forward and tell us the exact meaning of each field in its cookie. That would be a start.
Google analytics tracks your time on page, and is probably storing values to do with that when you lose focus on the page - this is used in analytics for showing site owners engagement etc. Re the pref cookie, it could well be to track your interaction with searches, as they do for site analytics, if it changes when you leave a page, that's the most likely explanation.
