Fix Unresponsive Script Warning

Posted: Monday, August 16, 2010 by El Guru in Blogs, Browsers, Firefox, Fx 1.5, Fx 2.0, Fx 3.0, Fx 3.5, Fx 3.6, Fx 3.7, Fx 4.0, Thunderbird, Tips & Tweaks

There are times depending on what is running in the background and other Internet activity that Firefox (or Thunderbird) may get bogged down and a JavaScript may take a little longer than normal to complete. Users will get a warning similar to the one below advising that the script is unresponsive.  The reason for this is because the application thinks the script is running wild and never going to finish processing thus causing the application to freeze and/or crash. This is very similar to Windows Task Manager warning you that an application is not responding, but the application is just a bit bogged down (which commonly happens with JavaScript) and needs more time to finish what it is doing.

The ‘fix’ for this is fairly simple, just increase the amount of time before a script is considered ‘unresponsive’. This can be done in both Firefox and Thunderbird via about:config (Firefox) and the Config Editor… (Thunderbird):


  1. In a new tab type about:config in the address bar and press enter
  2. In the about:config manager type dom.max_script_run_time in the Filter field
  3. Double click the entry and in the in the pop-up box type 20 and press enter
  4. Close the tab


  1. Go to Tools >> Options…
  2. Click on the Advanced tab on top
  3. At the bottom of the window is a section Advanced Configuration
  4. Click on the Config Editor… button at the lower right
  5. In the Config Editor… type dom.max_script_run_time in the Filter field
  6. Double click the entry and in the in the pop-up box type 20 and press enter
  7. Close the window

Source: Itchy Hands

  1. David says:

    Thanks a ton, this has been nagging me. I just fixed the timer so I haven’t had any more problems yet. I’m sure this is the cure!

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  6. Judith Little says:

    OMG! I got control over MY computer again! Thank you, thank you, thank you!!!! You were the only one who said to type about:config in the address bar IN A NEW TAB. It sure as @#$% didn’t work in the original one. Anyhow, I then got the warning about the warranty and i promised to be careful. Then I didn’t have to type in the filter field….a complete list of all the which-a-majigs ( I am not computer literate) came up. I just scrolled down to the one you identified, highlighted and double clicked it, then changed the 10 to 20. Guys have got to realize that their instructions are like recipes….leave the baking powder out of the cake and you get a brick!

  7. BreezyRacer says:

    Thanks a bunch! I have uninstalled/reinstalled FF, plugins, everything trying to kill this problem. Why did it crop up all the sudden? This info needs to be more widely disseminated.

  8. Amanda says:

    Tremendous! It worked, awsome…goodbye Mr Freeze!!

  9. TMB says:

    oooooh! thank you! thank you!…very clear instructions

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