Firefox will not start

This articles describes what to do if the Firefox window doesn't open when you click the Firefox icon.

• If Firefox starts but won't load any websites, see Error loading web sites.
• If you get error messages that indicate a crash, such as "Firefox has encountered a problem and needs to close", "Quality Feedback Agent", or "Mozilla Crash Reporter", see Firefox crashes.

Table Of Contents

• Extension prevented Firefox from closing properly
• Specific error messages
• Firefox is already running but is not responding
• There was an error launching the application
• The program must close to allow a previous installation attempt to complete. Please restart.
• Error opening file for writing...
• Firefox 3 will not start on OSX 10.3.9 or earlier
• Firefox 3 will not start on Windows 98/ME or earlier
• Firefox will not start after installing add-ons
• Firefox previously worked
• Firefox will not start on Linux

Windows:

Extension prevented Firefox from closing properly

Norton IPS, Norton Toolbar, and Skype 4.0 are all known to prevent Firefox from closing properly. Firefox is still running, but no windows are open.

1. Right-click on an empty spot in the Windows task bar and select Task Manager (or press Ctrl+Shift+Esc).
   
   
   
   
2. When the Windows Task Manager opens, select the Processes tab.
   
   
   
   
3. Select the entry for firefox.exe (press F on the keyboard to find it) and click End Process.
4. Click Yes in the "Task Manager Warning" dialog that appears.
   
   
   
   
5. Repeat the above steps to end any additional firefox.exe processes, if more than one entry is found, then exit the Windows Task Manager.
6. Start Firefox normally.
7. At the top of the Firefox window, click on the Tools menu, and select Add-ons.
8. Select the Extensions panel.
9. (If it is listed) Select Norton IPS and click Disable.
10. (If it is listed) Select Norton Toolbar and click Disable.
11. (If it is listed) Select Skype 4.0 and click Disable.
12. Click on Restart Firefox.

Specific error messages

Firefox is already running but is not responding

See Firefox is already running but is not responding for solutions.

Linux:

There was an error launching the application

This error indicates that either Firefox is not installed or your shortcut to it is incorrect. Make sure that Firefox is installed at the location specified by the shortcut. If it isn't, install Firefox if necessary, then modify the shortcut to point to the correct location.

Windows:

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

If you get a message saying The program must close to allow a previous installation attempt to complete. Please restart. when you start Firefox, see The program must close to allow a previous installation attempt to complete.

Windows:

Error opening file for writing...

If you receive the above error when launching Firefox on a Windows system, you may be required by Firefox to log in as an administrator. You can either reboot the computer or, if you have an administrator account, you can execute the program as an administrator.

1. Find the firefox.exe program file in the Firefox application folder on your system.
2. Right-click the icon.
   • (Windows XP) Select Run As.... Select The following user:. From the User name drop-down, select Administrator or another user that has administrator privileges. Enter the password required to log in to this account. Click OK.
   • (Windows 7 and Vista) Select Run As Administrator.... Complete a similar set of steps, as those listed above.
3. The Firefox application is started using the administrator Windows account. The user that was used to log in to Windows at startup is still the active one.

Mac OS:

Firefox 3 will not start on OSX 10.3.9 or earlier

Windows:

Firefox 3 will not start on Windows 98/ME or earlier

Mac OS:

Mozilla has stopped supporting OSX 10.3.9Windows 98/ME and earlier in Firefox 3.0 and higher. None of these operating systems are supported by AppleMicrosoft (and have not been for quite some time) and have multiple vulnerabilities that will remain unpatched. As such, you have the following options:

1. You can switch to another operating system. This is the most secure option. If you don't want to pay for a new operating system, you can get any of a number of versions of Linux which can run Firefox 3+ and can run on older machines. This ensures you have a completely secure system and access to all the great new features in Firefox 3+.
2. You can continue to use Firefox 2 which you can get from: our FTP siteour FTP site. Just because the browser will no longer receive security updates doesn't mean it will simply stop working. You will be using unsupported software on an unsupported operating system which poses a significant security risk.

Firefox will not start after installing add-ons

If Firefox previously worked but stopped after you installed extensions or themes, see Troubleshooting extensions and themes.

Firefox previously worked

If Firefox previously worked but suddenly doesn't start, it may be due to some corrupt data in your settings. Uninstalling and reinstalling Firefox would not fix this problem because your settings are not removed on uninstall.
To test to see if this is the problem, use the Profile Manager to create a new profile. If the problem goes away, you can then move your bookmarks and other important settings into the new profile.

Linux:

Firefox will not start on Linux

If you installed Firefox outside of your package manager, make sure that your system has the libraries listed in the system requirements.

Based on information from Browser will not start up (mozillaZine KB)