Youtube does that as well, and it has for a long time I guess, since I have been consistently able to reproduce the following: 1. open Youtube's home page in y

Youtube does that as well, and it has for a long time I guess, since I have been consistently able to reproduce the following: 1. open Youtube's home page in your main browser, while logged out and after clearing cookies 2. open the same page in a "virgin" browser (e.g. a newly created VM or even just using an incognito window) observe that 1 has some amount of "personalisation". When I saw this the first time I was baffled, so I did some research and found out that it's because of local storage. As per step 1, I was clearing just the cookies but not local storage. Lesson learned: don't just clear cookies, remember to clear local storage as well