Browser will not start up

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If Firefox or SeaMonkey fails to start, Your first step should be to restart the computer and then try again. If it still fails to start, then this article may help.

Browser process from previous session did not exit

If the Firefox or SeaMonkey browser process from the previous session did not exit properly, the next time you attempt to start your Mozilla browser it may fail to start with no error messages. Attempts to restart the browser may result in multiple instances of Firefox or SeaMonkey in the processes list. You will not be able to start the browser until you first end all browser processes or restart the computer. (If this is a recurring problem, read this for other possible solutions.) [1] [2]

Profile locked or inaccessible

One of the following messages can appear when you start your Mozilla browser if the profile is either "locked" or inaccessible:

  • Profile in Use: The Profile Manager appears along with a message that the selected profile is already "in use" when you attempt to start your Mozilla browser.
  • Close Firefox or Close SeaMonkey message box with one of these messages (using Firefox as an example): [3]
    • "Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system."
    • "A copy of Firefox is already open. Only one copy of Firefox can be open at a time."

In the above examples, ending the browser process or restarting the system will normally unlock the profile. If not, see the Profile in use article for further instructions.

Problematic extension or hardware acceleration prevents browser from starting

Try starting Firefox or SeaMonkey in Safe Mode (see the linked article for details). If the browser starts when you run it in Safe Mode, it's likely that an extension or, in Firefox 4 and above, hardware acceleration is causing the problem. See Problematic extensions and Firefox crashes#Extensions for more information.

Problematic plugin prevents browser from starting

Depending on your browser version and OS, Firefox or SeaMonkey may hang, crash, or simply fail to start because of a problematic plugin. If possible, visit Mozilla's Plugin Check page with another browser that Plugin Check supports (e.g., Safari or Opera) to help identify installed plugins. [4] Update all plugins, uninstall any plugins you no longer need or disable all plugins, to see if that resolves the problem. See Issues related to plugins for plugin locations and additional troubleshooting information, including how to disable plugins if your browser will not start.

The following plugins have been known to cause startup problems in Mozilla browsers:

  • "TrueSuite Website Log On" (AuthenTec) plugin. This plugin, related to certain fingerprint authentication and identity management software, may prevent Firefox from starting after rebooting the computer. Users report that reinstalling Firefox and, before a restart, disabling the plugin in the Firefox Add-ons Manager Plugins list will resolve the issue. You can alternately disable the plugin by finding and renaming the file "npffwloplugin.dll" as reported in this forum post. [5] [6] [7] [8]
  • "Facebook Video Calling Plugin". If installed, this plugin can prevent Firefox from starting, when you first try to launch Firefox after starting up your computer (you may need to click the Firefox icon 15 - 20 times before it starts). If you can start Firefox, disable the plugin in the Add-ons Manager -> Plugins list. To remove the plugin from your computer, see Facebook's uninstall instructions here. [9]
  • On Mac OS: Facebook Plugin "fbplugin_1_0_3.plugin". [10] "WebEx.plugin" and old versions of "huludesktop.webplugin" and "Flash Player.plugin" [11]

Startup issues after a Software Update

See the Software Update article for solutions to other problems after an update, if your specific issue isn't listed below.

XULRunner error after an update

If you see the message, XULRunner - Error: Platform version <x.x.x.x> is not compatible with minVersion <x.x.x.x> .... when attempting to open your Mozilla application after a Software Update, ("<x.x.x.x>" depends on version), use another browser to download the Firefox or SeaMonkey installer and save it to your desktop or other location. You should then delete the program folder for your Mozilla browser and run the installer you previously downloaded. For detailed Firefox instructions, see Standard diagnostic - Firefox#Clean reinstall.

This error is caused by inconsistent file versions ("application.ini" and/or "platform.ini" and possibly others). The problem may be a security program such as Zone Alarm Extreme Security (see below) that is preventing changes to your Mozilla application files after an update. [12] [13] [14] [15] [16] [17] [18]

Firefox does not start after updating with ZoneAlarm ForceField enabled

If you use ZoneAlarm ForceField (either standalone or as part of ZoneAlarm Extreme Security) Firefox may crash at startup or Firefox may fail to start after an update (you may see a message similar to Error: Platform version '9.01' is not compatible with minVersion > = 10.0 maxVersion < = 10.0 - see above). Try clearing the ZoneAlarm virtual cache (depending on ZA version, go to "Browser Security -> Settings -> Advanced" or "Internet -> Web Security -> Settings") then click "Clear Virtual Data" and restart Firefox. If you still can't start Firefox, turn off Forcefield (in ZA Extreme Security, go to "Internet -> Web Security -> Settings -> Advanced Settings", and turn off "Enable Virtualization"). If the problem persists, download the Firefox setup file from, remove the "Mozilla Firefox" program folder and then, with ZoneAlarm ForceField turned off, reinstall Firefox. If you need more help, contact ZoneAlarm Support. [19] [20] [21] [22] [23]

Computer must be restarted message after Firefox upgrade

If you see a message similar to Your computer must be restarted to complete a previous upgrade of Firefox after a major update (e.g., from Firefox 3.6 to 8.0) and restarting the computer doesn't help: On Windows, open the Mozilla Firefox installation directory (e.g., C:\Program Files\Mozilla Firefox or, on 64-bit Windows, C:\Program Files (x86)\Mozilla Firefox) and delete the file "firefox.exe.moz-upgrade", if found. Alternately, do a clean reinstall (use another browser to download the Firefox installer from and, after first removing the Mozilla Firefox installation directory, reinstall Firefox). [24] [25] [26]

"The program must close to allow a previous installation attempt to complete. Please restart." on Vista

If you are receiving this message when attempting to start Firefox and a restart has no effect, delete the “xpicleanup.dat” file, located in the C:\Users\<username>\AppData\Local\VirtualStore\Program Files\Mozilla Firefox folder. If you have problems finding or deleting this file, follow these steps:

  1. Restart your system, or if you know how, terminate all Firefox and xpicleanup processes with Task Manager.
  2. Go to "Start -> Start Search" and type in %APPDATA%.
  3. From there, navigate to Local\VirtualStore\Program Files\Mozilla Firefox
  4. Delete the file "xpicleanup.dat".

You should now be able to start Firefox. [27] [28]

If the problem persists, restart the system or use Task Manager again, then delete the "xpicleanup.exe" file in the Firefox installation directory (usually C:\Program Files\Mozilla Firefox). [29]

Procedure entry point js_SaveRegExpStatics error in js3250.dll after updating Firefox

Firefox may fail to start after updating and you may see the error, The procedure entry point js_SaveRegExpStatics could not be located in the dynamic link library js3250.dll. [30] As a workaround, open the Firefox installation directory (usually C:\Program Files\Mozilla Firefox) and look for two "js3250.dll" files (the second one will be named "js3250.dll.moz-backup"). Rename "js3250.dll" to "Xjs3250.dll" and then rename the backup file to "js3250.dll". This should allow Firefox to start but you will still need to update Firefox. Updating Firefox may resolve the issue but if the problem persists, download the Firefox setup file from, remove the "Mozilla Firefox" program folder and then reinstall Firefox.

Windows-specific problems

"Couldn't load XPCOM" error

This Firefox startup error can occur after performing a Windows System Restore (bug 877143) but whatever the reason, the usual solution is to do a clean reinstall by removing the Firefox program folder and then reinstalling Firefox (there's normally no need to uninstall Firefox before reinstalling it): [31] [32] [33]

  1. Use any browser to download the Firefox installer from and save the setup file to your computer.
  2. Delete the Firefox program folder, C:\Program Files\Mozilla Firefox (32-bit Windows) or C:\Program Files(x86)\Mozilla Firefox (64-bit Windows) by default.
  3. Reinstall Firefox by running the setup file you downloaded previously.

This error can also occur if you run Firefox in a "sandbox". For example, see this Avast forum thread and this Sandboxie forum thread.

No Mozilla applications will start

This can be caused by an incorrect setting in the Windows registry. If you attempt to install the Opera browser as a workaround, or if you attempt to install or remove various Microsoft applications, you will see an error similar to, Error 1606: Could Not Access Network Location. See this Microsoft support article for details, including a fix you can download. [34]

Firefox does not start when System Mechanic is installed

Firefox may fail to start if the Iolo System Mechanic application is installed. You may see an error message similar to: Firefox.exe - Application Error. The instruction at “0x5a9288f8” referenced memory at “0x5a9288f8”. The memory could not be “written”. (the memory address varies). Internet Explorer, Google Chrome, or other browsers may also fail to start. See if updating System Mechanic fixes the problem or, if don't need the program, consider uninstalling it. As a workaround, try disabling the two System Mechanic services. You can also try renaming the "ioloHL.dll" file in the C:\Program Files\iolo\Common\Lib folder. [35] [36]

Application fails to start because js3250.dll or other program files are missing

If you see message, This application has failed to start because js3250.dll was not found. Re-installing the application may fix this problem. you must reinstall Firefox (or other Mozilla browser) and check your system for malware. See This application has failed to start because js3250.dll was not found for more information.

"Error opening file for writing..." on Vista

Firefox may require you to be logged in as an administrator. As a workaround, to launch Firefox, right-click the icon and choose "Run As Administrator".[37][38]

Linux-specific problems


If you used "sudo" to install Firefox and it starts at the end of the install process and runs when you log in as root but fails to run as a normal user, then check the ownership of "$HOME/.mozilla" and subdirectories. The symptoms are that you won't get any error messages, and Firefox will exit with a value of 1. The ownership of "$HOME/.mozilla" and subdirectories may be set to "root:root", and you will need to execute

chown -R <username>:<usergroup> $HOME/.mozilla

at the command line to get Firefox to work (Firefox 1.0.x).

Similarly other users on the system may need their ".mozilla" folder 's permissions changed using "chown" as shown above.

Fedora 4 libstdc++

When you run from the console window the command /{path to download location}/firefox/firefox you may see

/usr/local/firefox/firefox-bin: error while loading shared libraries: cannot open shared object file: No such file or directories

On Fedora 4, you need to install libstdc++ by running yum install /usr/lib/ After running this, rpm -qf /usr/lib/ should print compat-libstdc++-33-3.2.3-47.fc4.

"/lib/i686/ version 'GLIBC_2.3' not found required by /{path to download location}/firefox/"

If you see

/lib/i686/ version 'GLIBC_2.3' not found required by /{path to download location}/firefox/

or something similar when starting Firefox, then the library is not new enough to support Firefox 1.5 and possibly previous versions. Updating GLIBC is not advised as other applications depend upon it. If possible, migrate to a newer Linux distribution with an updated version of GLIBC.

Mac-specific problems

Firefox won't run on Mac OS X when home folder is on a network share

Firefox 24 or above won't run (fails to start, opens with an empty browser window, runs very slowly, or stops responding) if the user home directory is stored on an AFP network share (bug 918612 - fixed in version 26). Note that reverting to Firefox 23 in such cases corrupts the profile. As a workaround, move the profile to the local startup drive. [39] [40] [41] [42]

Unable to reopen Firefox on Mac OS X after installing and closing it

A Mac OS X 10.8.4 user reported being unable to reopen Firefox after installing the latest version and then closing it. The only way to restart Firefox was to create a new profile (or remove all user profiles) and this needed to be done every time, otherwise Firefox would not start. See this thread on Apple's discussion forums for the solution, which was to follow a procedure that unlocks all user files (not system files) and resets their ownership and access-control lists to the default. [43]

Firefox 4 or above does not start on Mac OS X 10.4 or PPC Mac OS X 10.5

Starting in Firefox 4, Firefox requires at least Mac OS X 10.5 and will only run on an Intel Mac. If you install Firefox 4 or above on Mac OS X 10.4 or on PPC Mac OS X 10.5 it will not work. You may see an error message such as, You cannot use the application with this version of Mac OS X or, You cannot open the application "Firefox" because it is not supported on this architecture. Users with Mac OS X 10.4 or PPC Mac OS X 10.5 can install Firefox 3.6 after first removing Firefox. Another option is TenFourFox, which is based on Mozilla 2.0 and Firefox 4 code. [44][45] [46] [47] [48]

Firefox 3 does not start on Mac OS X 10.3.9 or below

Firefox 3 requires Mac OS X 10.4 or above. [49] Mac OS X 10.3 and 10.2 users can install Firefox 2 after first removing Firefox 3.

Other solutions

External links