Basic Troubleshooting

Most problems with Firefox can be fixed by following the troubleshooting methods described below. Try these in order.


1. Restart your computer

Sometimes problems can be fixed by simply restarting your computer and then starting Firefox again.

2. Clear your cookies and cache

Many problems with loading web pages can be resolved by clearing Firefox's cookies and cache:

1. At the top of the Firefox window, click on the Firefox button, go over to the History menu and select Clear Recent History....
   For Windows XP: At the top of the Firefox window, click on the Tools menu and select Clear Recent History....
2. In the Time Range to clear: drop-down, select Everything.
3. Click the arrow next to Details to display the list of items that can be cleared.
4. Select both Cookies and Cache.
5. Click Clear Now.

For more information, see Clear Recent History.

3. Update your plugins

Sometimes plugins for Firefox (such as Adobe Reader, Flash, Java, QuickTime, RealPlayer, and Windows Media Player) can cause problems. Often this is because they are out of date. To check to see if you have the latest versions of all your plugins, go to our Plugin Check page:

1. If any of your plugins are out of date, click Update and follow the instructions for updating that plugin.
2. After you've updated all of your plugins, restart Firefox
   • At the top of the Firefox window, click on the Firefox button (File menu in Windows XP) and then clickExit. Then start Firefox again.

4. Restart Firefox in Safe Mode

Safe Mode is a troubleshooting mode that disables all extensions, uses the default theme, turns off hardware acceleration, and uses default toolbar settings and controls, among other things. To start Firefox in Safe Mode:

1. At the top of the Firefox window, click the Firefox button, go over to the Help menu and select Restart with Add-ons Disabled.... Firefox will start up with the Firefox Safe Mode dialog.
   For Windows XP, click the Help menu and select Restart with Add-ons Disabled....

   Note: You can also start Firefox in Safe Mode by holding down the shift key while starting Firefox.
2. In the Firefox Safe Mode dialog, click Continue in Safe Mode.
3. Check whether your problem is still happening while in Safe Mode.

• If the problem still happens in Safe Mode, go on to step 5.
• If the problem does not happen in Safe Mode, see the Troubleshooting extensions and themes article and follow the instructions under The problem does not occur in Safe Mode to narrow down the cause.

5. Troubleshoot your plugins

Some problems can be caused by a plugin that no longer works with Firefox. To see if this is the issue, disable all of your plugins. If the problem goes away, it's likely that a plugin is the cause:

1. At the top of the Firefox window, click on the Firefox button (Tools menu in Windows XP), and then clickAdd-ons. The Add-ons Manager tab will open.
2. In the Add-ons Manager tab, select the Plugins panel.
3. Click each plugin in the list and then click Disable.
4. Check whether your problem happens when you have all plugins disabled.

If your problem goes away when all of your plugins are disabled, see the Troubleshooting plugins article to learn how to narrow down which one is causing it.

6. Reset your Firefox settings

Some problems can be fixed by resetting your Firefox preference settings:

1. At the top of the Firefox window, click the Firefox button, go over to the Help menu and select Restart with Add-ons Disabled.... Firefox will start up with the Firefox Safe Mode dialog.
   For Windows XP, click the Help menu and select Restart with Add-ons Disabled....

   Note: You can also start Firefox in Safe Mode by holding down the shift key while starting Firefox.
2. In the Firefox Safe Mode dialog, click to put a check mark by Reset all user preferences to Firefox defaults.
3. To apply your changes, click Make Changes and Restart.

7. Reinstall Firefox

Some Firefox issues can be caused by a problem with one of the Firefox program files. Follow these steps to completely remove and reinstall Firefox.

You might want to print these steps or view them in another browser.

1. Download the latest official version of Firefox from Mozilla.com.
2. Exit Firefox: At the top of the Firefox window, click on the Firefox button (File menu in Windows XP) and then click Exit.
3. Uninstall Firefox - see Uninstalling Firefox for instructions.
   During the uninstalling process, do not select the option to Remove my Firefox personal data and customizations. You will lose all of your bookmarks, history, passwords and settings.
4. After running the unistaller, be sure to also delete the Firefox installation folder which is located here by default: C:\Program files\Mozilla Firefox
5. Reinstall Firefox - see Installing Firefox on Windows for instructions.

Now start Firefox and check to see if your problem has been fixed. If it has, you can reinstall the extensions and themes you verified (in part 4 above) were not causing problems. If your problem hasn't been fixed continue with the next troubleshooting method.

8. Make a new profile

A bad profile can cause all kinds of problems with Firefox. To see whether your problem is caused by a bad profile, make a new one. If that fixes the problem, you can copy your data (bookmarks, saved passwords, etc.) over to the new profile.

1. Use the instructions in the Managing profiles article to start the Profile Manager and create a new profile.
   When creating a new profile, do not delete your old profile. You will lose all of your bookmarks, history, passwords and settings.
2. Once you've created a new profile, select it in the Profile Manager and click Start Firefox.

Test to see if your problem occurs with the new profile. If it doesn't, you can copy your data to the new profile - seeRecovering important data from an old profile for instructions.

Other solutions

If you've tried all of these troubleshooting methods and you're still having problems the issue may be with other software or your Windows system.

This section does not contain step-by-step instructions. For more information on any of these solutions, please check the related documentation.

Check for conflicts with your Internet security software

Some Internet security software (including antivirus, antispyware, and firewall programs) can cause problems with Firefox including blocking it from opening websites, crashes, and more. Often you can open the program's settings, remove Firefox from its list of allowed or trusted programs and it will be re-detected and things should start working again. If your program is listed at the Firewalls article, you can get specific instructions for how to properly reconfigure it.

Scan your system for viruses and spyware

Periodically, you should scan your system for viruses, spyware, or other malware. These free services are often useful:

• Malwarebytes
• Microsoft Security Essentials

Check your hard drive for errors

A problem with your computer's hard drive may prevent Firefox from running. Here are instructions for checking your hard drive:

• How to perform disk error checking in Windows XP on microsoft.com.
• Check your hard disk for errors on Windows Vista / 7 on microsoft.com.

Error loading web sites

This article contains information on diagnosing and fixing error messages that display when you try to view websites in Firefox.

Connection errors

Error messages that indicate connection problems:

• Unable to connect
• Server not found

If you experience one of these errors intermittently, check your Internet connection. If you connect wirelessly, make sure you are connected to the nearest access point and that the signal is strong.

If you experience one of these errors on some or all websites, see the following articles:

• Firefox cannot load websites but other programs can - if you can view websites in browsers other than Firefox.
• No programs can load websites - if you can't view websites in any browser.
• Cannot connect after upgrading Firefox - if you experience connection problems after updating Firefox.

Errors loading secure sites

If you experience an error accessing a website over a secure (HTTPS) connection, see the articles below that correspond to the error message you see:

• This connection is untrusted

• Secure Connection Failed
• Error code 500 accessing secure sites
• Could not initialize the browser security component

Interrupted or reset connection

The following error can occur if the website you're visiting is experiencing problems:

• The connection was interrupted
• The connection was reset
• The connection has timed out

If you can visit the website in other browsers but not in Firefox:

1. At the top of the Firefox window, click on the Firefox button, go over to the History menu and select Clear Recent History....
   For Windows XP: At the top of the Firefox window, click on the Tools menu and select Clear Recent History....On the menu bar, click on the Tools menu, and select Clear Recent History....At the top of the Firefox window, click on the Tools menu, and select Clear Recent History....At the top of the Firefox window, click on the Tools menu, and select Clear Recent History....On the menu bar, click on the Tools menu, and select Clear Recent History....
2. In the Time Range to clear: drop-down, select Everything.
3. Click the arrow next to Details to display the list of items that can be cleared.
4. Select both Cookies and Cache.
5. Click Clear Now.

Proxy errors

Error messages that indicate proxy problems:

• The proxy server is refusing connections
• Unable to find the proxy server

This error indicates that Firefox is trying to access the Internet through a proxy server. To check your proxy settings:

1. At the top of the Firefox window, click on the Firefox button (Tools menu in Windows XP) and then clickOptionsOn the menu bar, click on the Firefox menu and select Preferences...At the top of the Firefox window, click on the Edit menu and select PreferencesAt the top of the Firefox window, click on the Toolsmenu and select Options...On the menu bar, click on the Firefox menu and select Preferences...At the top of the Firefox window, click on the Edit menu and select Preferences...
2. Select the Advanced panel.
3. Select the Network tab.
4. In the Connection section, click Settings....
5. Change your proxy settings:
   • If you don't connect to the Internet through a proxy (or don't know whether you connect through a proxy), select No Proxy.
   • If you connect to the Internet through a proxy, compare Firefox's settings to another browser's (Such as Internet Explorer. See Microsoft's guide to proxy settings)(Such as Safari. See Apple's guide to proxy settings).
6. Close the Connection Settings window.
7. Click OK to close the Options windowClick Close to close the Preferences windowClose the Preferences window

Malicious website errors

If you receive one of the following errors, Firefox has blocked access to the website you're visiting to protect you from malware or web forgery (phishing).

• Suspected Attack Site!
• Suspected Web Forgery!

For more information, see Phishing and Malware Protection (Mozilla.com).

Other error messages

The ... plugin has crashed

This means that a plugin which is being used to display content on the current page has unexpectedly quit.

• See Plugin crash reports

Offline mode

Your operating system indicates to Firefox whether it is connected to the Internet. If it reports that it is not connected, Firefox will go into offline mode.If you see a message about offline mode, you may have set Firefox not to use your network connection. Make sure your computer has a network connection and then:

• At the top of the Firefox window,On the menu bar, click on the File menu and make sure that Work Offline is unchecked.

• At the top of the Firefox window,On the menu bar, click on the File menu and make sure that Work Offline is unchecked.Press the Alt key to temporarily turn on the Menu Bar, click on the File menu (Windows XP, just click on the File menu) and make sure that Work Offline is unchecked.

The page isn't redirecting properly

This problem can be caused by problems with cookies:

• See Websites say cookies are blocked.

File not found

If you experience this error when trying to access a local file (with a file:// URL), the path you are trying to access is either incorrect or inaccessible - verify the path.

If you experience this error trying to access a website, see:

• Troubleshooting extensions and themes
• Is my Firefox problem a result of malware

Content Encoding Error

The following error messages indicate a content encoding problem:

• Content Encoding Error
• The page you are trying to view cannot be shown because it uses an invalid or unsupported form of compression

Several problems can result in a content encoding error message. To diagnose and fix:

1. Check the settings of any Internet security applications you use (including firewalls, anti-virus or anti-spyware programs, and privacy protection programs). You should try to remove any permissions those applications have for Firefox, and then add them again. For program-specific instructions for a number of applications, seeFirewalls.
2. Follow the Standard troubleshooting steps.

This address is restricted

This error occurs when you are attempting to connect to a web server on a port that is reserved for another application.

If the web address (URL) you are trying to visit contains a colon followed by a number (e.g.http://webserver.tld:23), try removing that portion (e.g. http://webserver.tld) or replacing it with :80 (e.g.http://webserver.tld:80)

If specifying a different port does not work, you may have been given an incorrect web address.

Troubleshooting plugins

If you are having problems with pages that use plugins (such as Flash, Windows Media Player, Java, and more) to display content, you may need to check to see whether a plugin is causing the problem.

Common problems caused by plugins include:

• Crashing or Hanging
• Images or multimedia items do not load
• Problems downloading

Determining if a plugin is the problem

You can selectively disable plugins while Firefox is running. If you suspect a certain plugin, disable it first, then test for your problem. If you don't know which plugin to disable:

1. At the top of the Firefox window, click on the Firefox button (Tools menu in Windows XP), and then clickAdd-ons. The Add-ons Manager tab will open.
2. In the Add-ons Manager tab, select the Plugins panel.
3. Select a plugin in the list and then click its Disable button. Repeat this step for each plugin in the list. You do not need to restart Firefox for the changes to take effect.
4. Test for your problem. If it does not occur, go back to the Add-ons Manager tab and re-enable plugins one-by-one with the Enable button until you find which one causes your problem to occur.

If you find that disabling a plugin fixes your problem, continue following the steps in this article.

Updating or re-installing your plugins

Many problems with plugins can be solved by updating to the latest version of the plugin. To check if any of your installed plugins are out of date, visit the Mozilla Plugin Check page.

If updating to the newest version of the plugin or reinstalling it does not fix the problem, you can leave it disabled.

Manually uninstalling a plugin

If you can't use an uninstaller program to remove a plugin, you can remove it manually:

1. In the Location bar, type about:config and press Enter.
   • The about:config "This might void your warranty!" warning page may appear. ClickI'll be careful, I promise!, to continue to the about:config page.
2. Search for the preference: plugin.expose_full_path.
3. Double-click on the plugin.expose_full_path preference in the list to change the value to true.
4. Enter about:plugins into the Location bar to display the About Plugins page.
5. Each entry in the About Plugins page will have "File name:" followed by a path. Use Windows Explorer to navigate to the folder shown for the plugin you want to remove.
6. Rename the file to something other than its normal name - e.g. npswf32 becomes Xnpswf32

The plugin will be removed.

Re-initializing the plugins database

In some cases, you may not be able to install or re-install a plugin. Re-initializing the plugins database may fix this problem:

1. Open your profile folder:
   1. At the top of the Firefox window, click on the Firefox menu, go over to the Help menu (on Windows XP, click on the Help menu) and select Troubleshooting Information. The Troubleshooting Information tab will open.
   2. Under the Application Basics section, click on Open Containing Folder. A window with your profilefiles will open.
2. At the top of the Firefox window, click on the Firefox button (File menu in Windows XP) and then clickExit.
3. Delete the pluginreg.dat file.
4. Open Firefox
5. In the Location bar type about:plugins and press Enter to bring up the Firefox plugins list.