Mozilla launches Firefox's new caching back-end in Nightly version

Martin Brinkmann
Sep 23, 2013
Updated • Sep 23, 2013

Word about a new caching back-end for the Firefox web browser first spread when the lead designer of the project revealed that Mozilla was working on it in an attempt to protect the cache from crashes or kills of the Firefox process, and also to eliminate any caching related hangs.

The new caching back-end launched today in the latest Nightly version of the Firefox web browser.

It is interesting to note that it landed in desktop and mobile Nightly versions of the browser, and that it is turned off by default.

Interested Firefox users, and who would not be considering that they run the most cutting edge version of the web browser, can enable the new http cache of Firefox in the following way:

The new Firefox HTTP Cache

  1. Type about:config into the Firefox address bar and hit the enter key.
  2. Confirm that you will be careful if this is your first time opening the internal page.
  3. Type or paste browser.cache.use_new_backend into the search field at the top.
  4. Double-click the value and change it from 0 to 1 to enable it.
  5. Restart Firefox.

Note that you need the latest Firefox Nightly version for this. Make sure it is up to date if you do not get the preference listed here.

The preference has two values: 0 means it is disabled and the old caching back-end is used, and 1 means it is enabled so that the new cache is used by the browser.

Before you restart the browser, you may want to hear about other new preferences that have been added to Firefox in the wake of this.

  • The preference browser.cache.memory_limit defines the number of Kilobytes of cache that Firefox keeps in RAM to speed up page loading times and switching on the desktop. The default value is set to 51200 which is 50 Megabytes.

The lead developer notes that the system has some bugs currently. The disk cache is for instance not automatically cleared of old files if it is about to exceed its default limit. This needs to be done manually for the time being, but will be handled by Firefox automatically in the near future once the bug has been fixed.

Mozilla plans to enable the new HTTP Cache in the fourth quarter of 2013. It will still take several release cycles before it lands in the stable version of Firefox.

Closing Words

Most Firefox users should benefit from the new caching back-end performance-wise, or do not notice much of a difference if they work on a fast system (e.g. with a current generation Solid State Drive).

Performance is just one aspect however, and most users will certainly appreciate the fixing of cache related hangs and caching related issues when the browser crashes or is terminated in another way.


Tutorials & Tips

Previous Post: «
Next Post: «


  1. Erick said on June 13, 2015 at 3:20 am

    Hi Martin! Do you know why this (browser.cache.use_new_backend) isn’t enabled by default yet in currently versions of Firefox (currently 38)?

  2. Jones said on September 24, 2013 at 7:57 am

    I was a great lover of Mozilla few months back , but now i don’t like this , because it keeps me showing errors and gets crashed every-time . SO then i started working with Chrome and now i am happy with that .

    But now i will again try Mozilla , may be this time they have included some good features .

  3. some1uknow said on September 23, 2013 at 6:43 pm

    Is this in Firefox 25 Beta 1? Cause I have noticed pages render faster and it doesn’t seem to hang as much. Is it in UX Nightly as well?

    1. Martin Brinkmann said on September 23, 2013 at 6:52 pm

      This is only in Firefox Nightly right now. Not sure how often the UX Builds are updated, cannot answer that.

  4. Nhick said on September 23, 2013 at 4:22 pm

    Checking mine now and hopefully enable it correctly..hoping..

Leave a Reply

Check the box to consent to your data being stored in line with the guidelines set out in our privacy policy

We love comments and welcome thoughtful and civilized discussion. Rudeness and personal attacks will not be tolerated. Please stay on-topic.
Please note that your comment may not appear immediately after you post it.