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Firefox slow opening windows – here’s the secret

I’ve been having trouble for a long time with Firefox being damn slow to open new windows. I finally found the fix. Firefox hangs – MozillaZine Knowledge Base.

User Agent Switcher

Reinstallation or updating User Agent Switcher extension can cause hangs. Start Firefox in safe mode, uninstall the User Agent Switcher extension, and restart Firefox. You may now install the extension again without it hanging.

Instant improvement. Windows pop open in Firefox 1.5 under Mac OS 10.3 and 10.4. Not as fast as Safari but not bad at all.


  1. simone simone

    wow, i hope this is working

  2. origo origo

    Another secret to improving the speed of opening windows in Firefox is to minimize the number of extensions you have running. For every window that opens, all extensions are scanned and/or started causing alot of I/O operations that slow down opening of popup-windows.
    I run only Firebug and two other developer extensions, and I still think Firefox takes time opening windows (all this on WinXP).

  3. Origo, that’s a great tip. I do run a lot of extensions. Some of them are quite handy but I will clean house and disable a bunch of them and see if that speeds things up. My Firefox has gotten a bit slow again. Mainly since I installedFirebug, now that I think of it. I still find the venerable Web Developer nore useful as developers extension. Perhaps I just am more used to the Web Developer toolset.

  4. Yes, the point about loading all the extensions for each new window means that it’s typically much faster to open a URL in a new tab than a new window.

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