Workaround for Firefox 3.5 slow startups on Windows

If you find yourself with very long startup times after upgrading to Firefox 3.5 (from say 10 seconds to the order of minutes), you may be experimenting a bug due to a change in how Firefox 3.5 gets the randomness it needs for security purposes on Windows.

The procedure involves scanning some temporary folders looking for bits normally added by OS and other applications operations. Firefox 3.5 looks for more files and deeper (more subfolders) for increased randomness, but it has led to unexpected results for users with too many temporary folders or files resulting in slow startups.

Try builds are still being generated with fixes to this bug, but users report a noticeable improvement after deleting their temporary folders and  Internet Temporary Files (generated by Internet Explorer).

To clean temporary folders, check  and delete all files [you can, some may be in use] from these:

C:\Documents and Settings\*user*\Local Settings\History
C:\Documents and Settings\*user*\Local Settings\Temporary Internet Files
C:\Documents And Settings\*user*\Local Settings\Temp
C:\Documents And Settings\*user*\Recent

On Windows Vista /7:

%USERPROFILE%\AppData\Local\Microsoft\Windows\Temporary Internet Files

To delete Internet Temporary Folders, in the Control Panel., open Internet Options. In the Browsing History section, press the Delete… button, check all the options and press Delete.

IE 8 Delete Browsing History

Users report a significant improvement after doing this, even those who use Internet Explorer once in a while.

A fix to this bug should become available with Firefox 3.5.1, expected in a few weeks.

Edit: Thanks to Dan in the comments I’ve updated the post with the correct Windows Vista/7 paths for temporary folders.

102 thoughts on “Workaround for Firefox 3.5 slow startups on Windows”

  1. See my post above of Aug 31. I really think this is the best solution until F Fox comes up with something we can all applaud. If anyone has some better idea, pls announce it!!!!

  2. I could NOT work another day with the slow Firefox issues…

    So had to stop working long enough to research if others are having the SLOW issue, and the OTHER issue – that it takes often over a minute for FF to close once I shut it down (close the browser).

    It’s a little comfort to read that I’m not the only one battling with and suffering from these FF bugs. I’ve been deleting History, temp files, etc. No affect whatsoever. Updated to latest version. No better. In fact, Its just getting worse. It’s gotten so bad I’ve gone back to IE for now.

    Any idea of WHEN these Firefox bugs are going to get fixed, for real?

  3. Here is my situation:
    Defragged disk, ran Disk Clean and CCleaner, turn off FF ipv6 DNS, turn on FF pipeline (8 max), lots of other misc cleanup. Never had skype or FF Preloader. I installed AFOM 2.0 experimental addon for firefox memory leaks.

    Reasonably fast startup after all this work, considering I have a dozen addons and 18 tabs.
    Still slow FF shutdown – about 1 minute per Task Manager :-(
    Still slow scrolling, browsing.

    Two of my tabs are YouTube, and Task Manager shows 40-50 I/O Reads per second for each. I know, because when I close the YouTube tabs, the I/O Reads stop immediately. They must be memory I/O since the disk I/O light is off, and StatusbarEx addon shows no network activity. Also the liveHTTPheaders plugin shows no new web page headers. If I start or restart the video the I/O Reads go back to normal, enough to play the video I guess. If I pause the video, the I/O Reads go to zero. If I let the video finish playing, and don’t do anything else, I get the 40-50 I/O Reads per second again, forever. Using the QuickJava addon to turn off JavaScript and Java has no effect on any of this.

    Even with all these addons and tabs, StatusbarEx and Task Manager both report that FF is only using 60-70Meg. However, before I started all this cleanup, it sometimes got up to 300-400Meg of memory, and took much longer (several minutes) to finish shutting down. I suspect the Youtube tabs and I/O Reads had something to do with that, too.

    I wish there was a FF addon that told me which tabs were using the CPU or generating I/O.

  4. I have found that my problems were caused by my back-up software. I use a ‘cloud’ backup system which is always on and it was incorrectly backing up the temporary directories mentioned above. Once I removed these from my back ups Firefox was back as a decent piece of software! Hooray!

  5. I will stick with FF although it has issues, it crashes, has a bad start up time and works bad with shock wave flash 10. Sad I could not get alternative to shockwave.

    Anyway people we left an evil empire and certainly cannot go back to another evil empire. Stay with FF.

  6. Firefox 3.5 slow startups on Windows

    Modify the Firefox config file: Here’s some tweaks which involve modifying the config file for Firefox. I’d heard some of these a while ago on the Mike Tech Show podcast, also at Life Rocks 2.0. It’s not difficult to edit the config file. Just type about:config in the Firefox address bar and press enter. Then type network.http in the filter field. This will filter the list down to only those with network.http in the name. Now make the following changes:
    • Double click on ‘network.http.pipelining’ and set the value to true (double clicking toggles the value between true and false).
    • Double click on network.http.pipelining.maxrequests’ and in the dialog box enter a value higher than the default value 4. According to Mozillazine, the maximum you can use is 8.
    • Double click on ‘network.http.proxy.pipelining’ and set the value to true.
    • Again in the filter field enter ‘browser.sessionstore.interval‘ (without the quotes), double click on the entry and change the value from 10000 (10 secs) to 120000 (2 minutes). This adjusts how frequently Firefox creates session restore save points. Firefox will now take a snapshot of your browsing session every 2 minutes instead of every 10 seconds.
    • Right click on the page and select New->Integer. Enter the name nglayout.initialpaint.delay and then click ok. Set the integer value of this to 0 and click ok.

  7. Firefox – sadly – is nearly useless now. Where once it was fast to load, fast to grab pages, and a pleasure, even a joy to use, it now takes 16 or 17 years to load (or so it seems), sees to debate with itself overr whether it really does want to bring up a web page or not before slowly doing so, and has become painful to use even in the best of circumstances – no matter how I tweak it.

    A real shame. It was a good program once. Very good. Now, even IE looks good in comparison to it, and Chrome a joy..

    R.I.P., Firefox.

  8. Forgot to add that wish FF kept two versions. A fancy one for people who need all the bells and whistles and a simple lean and efficient browser for others.

  9. Like everyone else here, I was on the point of ditching FF 3.5.2 and reverting back to IE because of the ridiculous startup times. As a last effort I tried following Herminio’s tweaks above – they work!
    Don’t know why exactly but I used 8 for “pipelining” and speeds are as fst as they were in FF 2.0.
    I’m happy again – thanks Herminio, you’ve made a difference in the world, be proud!

    1. I have switched to Google Chrome. No probs so far. It is super fast, does everything I want it to do and saves all my settings, bookmarks, bookmark toolbar etc. Noi more F Fox for me. I have work to do!

  10. Thanks Herminio – those config settings did the trick for me too,
    deleting the temp files made no apparent difference

  11. The thing I don’t get is this… if FF is looking at these temporary files to get randomness and the recommended slowness fix involves deleting the temporary files, aren’t we wiping out the method that FF is using to get it’s randomness? I mean, if the only way to get something working is to prevent it from working, surely something is very wrong with the concept in the first place.

  12. Hi all,
    I have tried all the above suggestion to no avail. After hours of struggling I noticed that I had two Mozilla Firefox installed in my machine: One on C: and other on D:.
    So here is what I have done to solve the annoying slowness:
    1- Uninstall any MF from Control pannel
    2- Search for any word like *mozill*.* in your machine and remove it (some mozilla files can’t be removed from some plugins folder but It’s ok)
    3- Download and install the latest version of MF (currently 3.5.6)
    4- Make sure to install it under C:\Program Files

    Now my MF is extremely fast and I even set it as my default browser.


  13. Quote: “Download and install the latest version of MF (currently 3.5.6)”
    Riiiight. Do your weekly firefox uninstall/download/reinstall/uninstall/reinstall/ repeat. What ever happened to code it right the first time and TEST before releasing to the public. How can you people tolerate quick and dirty software releases.

  14. Unfortunately firefox is simply not ready for worldwide domination. It still behaves like a concept car, nice to look at, but doesn’t really work that well. I have been using it on 10 different machines for 13 months and it is a piece of promising software but that’s all. I just rang a company becuase I could navigate to some pages- guess what? It was firefox’s fault as it worked beautifully on IE6/7/8 and opera! Seriously, all I want is the speed of IE6 without all the security issues- is that too much to ask? IE7 and IE8 are way to slow and too bloated. Opera is just a funny little cute browser but not practical enough and has issues with touchpad scrolling across all my machines- enough to ditch it too.

    1. I’ve gone back to IE8. Every time I have to load FF either manually or through a link, it is a minimum of 30 seconds to load on my Windows 7 machine. It is now completely unusable for this reason.

  15. Well, Firefox was a nice program but it has been destroyed. The slow startup is unacceptable. There was a chance for this program to become the dominant browser. I wonder if a spy from microsoft or google has infiltrated the firefox team and is sabotaging the product?

    please, back to basics.

    1. appears the problem is due to a conflict with my old version of symantec antivirus.

      ran system mechanic, unistalled symantec products, now FF 3.5 works like a charm.

  16. FF has to strip down to the older versions. It has become too heavy of an application, not something you need in a browser.

  17. I have 3 computers running:

    xp biz desktop 3gb mem… runs almost instant startup on firefox

    vista laptop 3gb mem… runs almost instant startup on fire fox

    xp desktop (only 1gb mem)… others browsers (safari, opera, start up in about 10 seconds… ie7 about 30seconds…

    now: I understand the limited mem of this machine would mean slower starts overall then the other two that have 3gb mem… but Firefox USED to start up quickly… I did the suggested fixes… mostly deleting ie7’s “history and temp files” and that IMPROVED THINGS… but just marginally…THEN I FOUND THE SOLUTION (at least for me)…

    and it is: THE AVG ANTIVIRUS “ADD-ON” …I disabled that in the add-ons…and now Firefox starts up in about 5 seconds… before this step it took minutes… (also, I was already using FasterFoxLite… which I had tried with little noticeable improvement… basically I disable MOST ADD-ONS…except java stuff, Fireshot (for quick screen or webpage cys), StumbleUpon… in other words on only keep ENABLED in the ADD-ONs…stuff I USE A LOT.

    on my 3gb mem machines…this doesn’t matter…but check if you have an antivirus like AVG running as an addon— I have the free version…very good…but in this situation… all but prevents me using Firefox…

    Safari, and Opera… are very good too…almost as quick and similar in mem usage to Firefox… but I like StumbleUpon and Fireshot too much, so I do want to mainly use Firefox…AND NOW IT’S ALMOST INSTANT STARTUP!

    hope this helps many,


    flashrob (website: if your interested)

  18. We are april 2010 now, and Firefox is at version 3.6.3.

    It became even slower. Not only startup-time, but normal use too.

    It’s useless this way.

    Did Microsoft buy Firefox?

    IE is better now, a lot (and I tought I would never say this).

  19. This “work around” did not work for me. Besides, In our production environment there is little time to experiement with “work arounds”.

    Until Mozilla fixes this problem, I am going back to IE8. It seems to work fine without “work arounds”.

    Notify me when the problem is fixed.

  20. Firefox does start slow , just fine tune like a car ,add /PREFETCH to th e reg. key and see the diffrence,, (HKEY_CLASSES_ROOT\Applications\firefox.exe\shell\open\command
    Default, REG_SZ “C:\Program Files\Mozilla Firefox\firefox.exe” %1″ /PREFETCH).. now it loads in approx. 0.5 sec.

    OS Name: Microsoft Windows XP Professional
    OS Version: 5.1.2600 Service Pack 3 Build 2600
    This also works on Adobe Acrobat loads in approx. 0.7sec..

    I hope this helps someone….

    1. I should have said that there is a space after the parenthesis mark (“) then add /PREFETCH .. It works better in Capitals because the program thinks you are yelling at it (A programer thing)

    2. Looks like a bullshit.

      1. With a “factory-set” (both sets are enabled) Prefetch the Prefetch Cache populates with a FF prefetch data w/o any commandline switch.
      2. AFAIK the “/prefetch” switch used *only* with an additional “:” (or “=”, I don’t remember) ending like “app.exe /prefetch:2″ and useful only when a some app loads (and don’t mixes) a mostly different set of DLLs for a different tasks (compare a reg commandlines of a wmplayer.exe for audio- and dvd- content)

  21. Ed – Can’t say I’ve noticed FF crashing, if anything it appears more stable than previous versions, but I still have a memory leak that I’e had in FF since v1.5!
    What I have noticed though is that after a restart, FF takes about 20 seconds to load, if you close it again and start a new FF it comes up in about 3 seconds. I don’t know if this is FF or my firewall (Comodo) or anti vius (AVG) causing the initial delay in checks – still to try and determine that one. Generally though 3.5.2 appears to be stable.

Comments are closed.