Now go to https://rittervg.com/misc/ff/fpi.html
On first load it should say the same.
If it says the same timestamp that was stored on the first page - it's not working.
Source: I'm a Mozilla Developer who is one of the primary devs/supporters of First Party Isolation.
Thanks for diagnosing that for me, you're right blocking third party cookies does cause it to fail.
Both tests are equally valid. I just gave one because trying to be exhaustive about testing it would be mind-numbing. The test I provded only does localstorage, but FPI also isolates DNS cache, H2, image cache, favicons, cookies, localstorage, indexdb, etc etc
Safari by default has a stricter storage access policy by default for all third-party domains, which requires you to visit the domain as a first party first. So it's probably that rather than ITP.
I have a general question if you don't mind. I use Firefox Beta. Why is Firefox going the route of a manual blacklist (disconnect) instead of working on some kind of programmatic machine-learning/somewhat intelligent third-party storage blocking by default that doesn't discriminate known against unnkwon trackers?
Seems to be working, thanks! (had to disable blocking of third-party trackers for it to function, but after that, it works as promised, and I have re-enabled blocking of third-party trackers)
So wouldn't a better test be about a third party that was used in a first party context before? Since FPI goes beyond third party cookies.