Tweak Firefox’s "Responsiveness" Config Setting

By Lowell Heddings on January 22nd, 2008

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
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