I have updated my Ubuntu 14.04 recently and got a new firefox (version 35.0). I have configured an empty starting page and my default search engine is configured to duckduckgo.

but: Since the update I get a google.com cookie called "PREF". When I remove that cookie, close firefox, and open firefox again, the cookie is back again.

Where does this cookie come from? How can I avoid that this cookie is set?


I did a small experiment: When I cut the network connection during the launch of Firefox, no Google cookie is set. So the real question is: Why is Firefox 35.0 contacting Google when I don't ask it to do so?


There are two ways to avoid this cookie to be set:

  1. In the Security tab of Firefox's Preferences uncheck "Block reported attack sites" and "Block reported web forgeries".

If one of these two options is activated, Firefox contacts Google to load lists of websites, which should be blocked and this cookie is set.

If you still want to use these options, but instead blocking only that cookie, there is the second method:

  1. Go to the Privacy tab and change History settings in the drop down menu to "Use custom settings for history", then some options show up. See the option "Accept cookies from sites" and to the right side of that option the button "Exceptions..." - click it and a new dialog box appears. Enter "google.com" into the text area labeled "Address of website:" and click the button "Block" under that text area.

For me, both ways prevented the cookie to being set again.

  • Unfortunately, this is not the answer I am looking for. My real question ist: Why is Firefox 35 knocking on Google's door at start? – jk - Reinstate Monica Feb 5 '15 at 9:27
  • This in fact is answered in my original answer: "[...] Firefox loads lists of websites to be blocked from Google [...]" – Frank Drolshagen - f.d.g. Feb 6 '15 at 12:43
  • 1
    To make it (hopefully) more understandable I edited my original answer. – Frank Drolshagen - f.d.g. Feb 6 '15 at 12:55

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