The current Tor browser bundle (3.6.3) appears to be based on Firefox at version 24.7.0.

Is this an independant Tor browser version, unrelated to the latest Firefox version (31.0), or the version of Firefox on which the Tor browser is based?

Is the Tor browser kept up-to-date with the latest Firefox browser?

If not, can one "Tor-ize" the latest Firefox browser upon each new release?


1 Answer 1


The Tor Browser Bundle (TBB) uses Mozilla Firefox ESR.

Mozilla will offer an Extended Support Release (ESR) based on an official release of Firefox for desktop for use by organizations including schools, universities, businesses and others who need extended support for mass deployments.

Since TBB has the goal to be secure and stable, it uses the ESR version, not the latest and greatest Firefox. The TBB is regularly updated with the latest version of Firefox ESR.

About the difference to the "normal" Firefox:

Users who want to get the latest features, performance enhancements and technologies in their browsing experience should download Firefox for personal use, as these improvements will only be available to ESR users several development cycles after being made available in Firefox for desktop.


On August, 12th 2014 Tor Browser 4.0-alpha-1 was released. Part of the release notes for this version is:

  • Update Firefox to 24.7.0esr

This is an example of how the Tor project keeps track of the latest versions of Mozilla Firefox ESR.

Edit 2

Mozilla Firefox ESR 31.0 is too young to be included in the TBB. It is not out of the "qualify" phase for a new ESR. See the life cycle chart at Mozilla.

enter image description here

  • 1
    the only issue with this logic is, that Firefox 31 is a current ESR
    – JimiDini
    Aug 14, 2014 at 11:55
  • "The latest" doesn't mean "release two weeks ago".
    – user66
    Aug 14, 2014 at 11:58

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .