How-To Geek

Tweak Firefox’s "Responsiveness" Config Setting

Have you ever noticed that sometimes Firefox isn’t very responsive while loading a page? As a frequent StumbleUpon user, this behavior grates on my nerves so I went looking for a solution.

When Firefox is loading a page it uses one of two modes: There’s a high priority mode that doesn’t pay as much attention to your mouse and keyboard, but loads the page faster. There’s also a lower priority mode that interrupts the parser more often to respond to input events. It’s even documented at Mozillazine.

What we can do is tweak the amount of time before Firefox switches from lower priority mode back into high priority mode.

Type about:config into the Firefox address bar, and then filter by the following:



Most likely the key doesn’t exist yet, so you’ll have to set it by right-clicking in the empty area and selecting New \ Integer. Use these values when prompted:

  • Key Name: content.switch.threshold
  • Key Value: 1000000

The default value is 750000, or 3/4 of a second. The more time that you tell Firefox to wait before resuming high priority mode, the more responsive the application will feel… but it will obviously take a little longer to load the pages. You could reverse this if you were more worried about speeding up page load time.

Note that this setting only works if you haven’t changed content.interrupt.parsing to false.

Lowell Heddings, better known online as the How-To Geek, spends all his free time bringing you fresh geekery on a daily basis. You can follow him on if you'd like.

  • Published 01/22/08

Comments (19)

  1. Lisaweb

    Sweet! Just entered the settings, and wow! What a difference it makes. My browser is no longer freezing. Great tip! Thanks Geek!

  2. abolhood

    neither content.switch.threshold nor content.interrupt.parsing are showing in my config!!!! how can i find them or do this thing?
    Am using FF 3b2


  3. KS

    Hmm. I don’t have that entry in my about:config? Any idea why?

  4. The Geek

    The key is not created by default, you will have to create it using the instructions above.

  5. KS

    Duh. Maybe I should read the whole thing next time. Sorry guys. Great job!

  6. John Kiely

    Wow that is fantastic, speeds up Firefox more than I thought!
    What a great site I am browsing here more often !!!

  7. Guru

    good to know info Please keep it up; any place where I can do a donation?

  8. The Geek


    No need to donate, we provide you information for free. If you feel you need to give back, then share the article or the site with your friends =)

  9. Cant Live without FireFox

    i try to figure out why my browser is so slow, and this article really helps alot.. my browser now is doing great. thanks sir.

  10. Louis Liem

    I’m stumbling it :) !

  11. jim

    This is the version of firfox that I am using and it does not work.


    Also is there a way to get rid of the page that says I have been updated to the new version of foirFox?

  12. Greg

    I played around with the numbers to see if i prefered to tweak the number higher or lower. I have it set to just 100000 (one hundred thousand for those of you counting the zeros) and WOW is it ever faster!
    Great find!

  13. n00b

    I did something stupid and added a new key name 750000. Is there a way to delete keynames?

  14. Ed

    I would like to load stumble in Firefox browser. Reloaded Firefox and stumbleupon numerous times.
    Most current versions.

    Need your help —Please

    Thanks Ed

  15. Leandro

    If I have a supercomputer, should I set content.switch.threshold into high priority mode to load more quickly the page?

  16. irene

    thank u all..
    now i can smile using my firefox
    thanks a lot

  17. John Mack

    I changed this setting before in an older browser but had forgotten about it. It really does improve download performance when it is set to a lower value.

  18. John Mack

    This setting is so important Firefox should allow users to change it without having to go into “about:config.” (how many average users even know “about:config”?) Firefox should notify users of the default value and what happens when the value is increased or decreased and let users determine what’s best.

  19. kizza

    are there more tweaks? i tweaked once and had to reset. would appreciate having all the tweaks. thanks

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