Some days ago I noticed that YouTube knows the videos I watched even though I deleted my cookies. I also was not using a YouTube-account. When I noticed I used IE 11. After some research I found out that YouTube uses zombie cookies. For those who don't know: zombie cookies are cookies that don't get deleted if you use the "delete cookies"-function in your browser. In most cases they are flash cookies and you have to delete those to "kill" these zombie cookies.
But even after deleting my flash cookies YouTube still knew the videos I watched (I tested that in most cases on this site: https://www.youtube.com/feed/history This site shows you, how many videos you watched so far).
So my question is: How is YouTube identifying my, even after deleting flash cookies? How can I can delete the information YouTube has of me?


I do the following to force youtube to "forget" me.

  1. Use firefox (just because I think it's better, but this shouldn't be required)
  2. Configure flash to not store any data (right click on a flash app/video, select global settings, storage tab -> "block all sites from storing information on this computer")
  3. Now when you delete the cookies, google won't be able to re-create them from any flash data.

If you do want to allow some sites to store data in flash, you can block just one site. The reason why google can rebuild the history is (probably) because it has the data both in web cookies and flash cookies, so as long as one is present when you visit youtube, google can rebuilt the other cookies.

Source: I just tried this :)

  • With IE ensure that you can view Hidden Files when you're clearing cookies. Some of the cookies are hidden this way. – RoraΖ Aug 20 '14 at 12:05
  • @raz For some reason it didn't work. I configured flash and deleted IE cookies, but this didn't help. What exactly do you mean by "hidden cookies"? Or could it be that YouTube also uses my IP-address to find me? (I deleted cookies and checked YouTube directly after that) – Sirac Aug 21 '14 at 12:09
  • I only meant that IE will sometimes change the permissions of the cookies to be on the level of system files or "hidden files". So if you're manually removing them, if you don't have "show hidden files and system files" option enabled in your Window view you won't see them. – RoraΖ Aug 21 '14 at 19:17
  • @raz I used the "delete cookies" function of IE itself, but now that you mentioned it: When I was looking into the cookies folder of IE there were too many cookies than they should be. I just deleted cookies and started IE, so there should only be cookies of google.com. I didn't delete them because a strange warning popped up when I tried to. could it be that IE saves the cookies of my favourite sites and does not delete them? – Sirac Aug 26 '14 at 9:46
  • Your answer is completely right, but I still have problems to make that happen for IE. I guess, if you want to browse private, you shouldn't use IE for anything... – Sirac Aug 30 '14 at 0:57

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