Firefox hangs or is not responding - How to fix

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  • Creator: Bo102010
  • Comment: Fix Go menu
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When a program hangs, it no longer accepts user input and does not seem to be performing any actions. Other terms for hanging are "freezing" or "not responding".

  • A hanging program is different from a program that has crashed; a crash ends the program.
  • A hanging program does not respond to your actions. In other situations, Firefox responds to your menu and button actions but fails to load any websites.

To resolve hanging problems not specifically mentioned in this article, or if the suggested solutions do not solve the problem, see Troubleshoot and diagnose Firefox problems. You should also scan your computer for viruses, spyware, and other malware and read Troubleshoot Firefox issues caused by malware.


Hang loading first window

A Firefox hang while loading the first browser window may be caused by "hyper-threading". A feature on some Intel Pentium 4 processors, hyper-threading is designed to improve performance, but it can also cause Firefox to hang.

If your computer has an Intel Pentium 4 processor and you use Windows 2000 and XP, you can disable hyper-threading for Firefox:

  1. Right-click the shortcut icon you use to start Firefox.
  2. Select Properties.
  3. Select the Compatibility icon.
  4. Select Run this program in compatibility mode.
  5. In the drop-down for compatibility mode, select Windows 98/Windows ME.
  6. Click OK.
  7. Restart Firefox to see if the hanging has gone away.

Hang loading every window

The SwitchProxy Tool extension checks for updates each time a new window is opened. This is a known issue.

If you use SwitchProxy Tool, you can disable it to see if hanging is prevented:

  1. At the top of the Firefox windowOn the menu bar, click the Tools menu and then select Add-ons. The Add-ons dialog appears.
  2. Select the Extensions panel. The list of installed extensions is displayed.
  3. Select SwitchProxy Tool.
  4. Click Disable.
  5. At the top of the Firefox window, click on the Firefox button and then select ExitAt the top of the Firefox window, click on the File menu and then select ExitOn the menu bar, click on the Firefox menu and select Quit FirefoxAt the top of the Firefox window, click on the File menu and select Quit

    Click the menu button New Fx Menu and then click ExitQuit Close 29

  6. Restart Firefox. Open several new windows to see if Firefox no longer hangs.

Hang downloading files or saving images

If Firefox hangs when you attempt to download a file or save an image, try these solutions:

Clear download history

Firefox may hang when downloading files if your download history has grown too large. To clear the download history:

  1. At the top of the Firefox windowOn the menu bar, click the Tools menu and then select Downloads. The Downloads window will open.
  2. Click Clear List. The download history is cleared.
  3. Download some sample files to see if the hanging has stopped.

Choose a different download folder

Firefox may hang if the last download folder location (e.g. a shared volume or USB drive) is no longer available. To fix this:

  1. At the top of the Firefox window, click on the Firefox button and then select Options.At the top of the Firefox window, click on the Tools menu and then 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.

    Click the menu button New Fx Menu and choose Options.Preferences.

  2. Select the General panel (Main panel in Firefox 3.5).
  3. In the Downloads pane, select Save files to and click the Browse button.
  4. In the Browse For Folder window, choose a new folder location.
  5. Click OK to close the Options window.Click Close to close the Preferences window.Close the Preferences window. Close the about:preferences page.

See if you are now able to download files or save images. If this works, you can go back to your Firefox settings, if you wish, and select Always ask me where to save my files.


Hang opening the History menu or the History sidebar

Firefox may hang when using the History menu or sidebar if your browsing history has grown too large. To fix this issue, clear the browsing history:

  1. At the top of the Firefox windowOn the menu bar, click the Tools menu and then select Clear Private Data.... The Clear Private Data dialog appears.
  2. Deselect all boxes except Browsing History.
  3. Click Clear Private Data Now. The browsing history is cleared. See Clearing private data for more information.

To prevent a recurrence of this issue, you can configure Firefox to retain a smaller browsing history, in the Settings for privacy, browsing history and do-not-track:

  1. At the top of the Firefox window, click on the Firefox button and then select Options.At the top of the Firefox window, click on the Tools menu and then 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.

    Click the menu button New Fx Menu and choose Options.Preferences.

  2. Select the Privacy panel.
  3. In the Keep my history for at least XX days text box, enter a value that is less than the current one. This value defines the number of days that Firefox retains browsing history; a lower figure should result in less retained browsing history.
  4. Click OK to close the Options window.Click Close to close the Preferences window.Close the Preferences window. Close the about:preferences page.

  1. At the top of the Firefox windowOn the menu bar, click on the Tools menu, and select Clear Recent History....
  2. In the Time range to clear drop-down menu, select Everything.
  3. Click the button next to Details. A list of history items will be displayed.
  4. Select Browsing & Download History.
  5. Click the Clear Now button. The Clear Recent History window will close and your browsing history will be cleared, as well as the Download history. See Delete browsing, search and download history on Firefox for more information.

To prevent a recurrence of this issue, you can configure Firefox to retain a smaller browsing history, in the Settings for privacy, browsing history and do-not-track:

  1. At the top of the Firefox window, click on the Firefox button and then select Options.At the top of the Firefox window, click on the Tools menu and then 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.

    Click the menu button New Fx Menu and choose Options.Preferences.

  2. Select the Privacy panel.
  3. Beside Firefox will:, make sure Use custom settings for history is selected, if it isn't already set.
  4. In the Remember my browsing history for at least XX days text box, enter a value that is less than the current one. This value defines the number of days that Firefox retains browsing history; a lower figure should result in less retained browsing history.
  5. Click OK to close the Options window.Click Close to close the Preferences window.Close the Preferences window. Close the about:preferences page.

Hang loading websites

Automatic proxy configuration file

If you're using an automatic proxy configuration file (PAC), Firefox may hang when you attempt to load sites that don't exist or that you haven't opened recently. To determine if you use an automatic proxy configuration file:

  1. At the top of the Firefox window, click on the Firefox button and then select Options.At the top of the Firefox window, click on the Tools menu and then 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.

    Click the menu button New Fx Menu and choose Options.Preferences.

  2. Click the Advanced icon.
  3. Click the Network tab.
  4. Click Settings. The Connection Settings dialog appears.
  5. If Automatic proxy configuration URL is selected, you are using an automatic proxy configuration file. Do not disable this setting, which will prevent you from accessing the Internet. Instead, provide this link to your network administrator.
  6. Click Cancel.

Duplicate Session Restore files

Firefox may be be slow to respond or hang if multiple copies of its Session Restore file have been created:

  1. Open your profile folder:

    At the top of the Firefox window, click on the Firefox button, go over to the Help menuOn the menu bar, click on the Help menuAt the top of the Firefox window, click on the Help menu and select Troubleshooting Information. The Troubleshooting Information tab will open.Click the menu button New Fx Menu , click help Help-29 and select Troubleshooting Information. The Troubleshooting Information tab will open.

  2. Under the Application Basics section, click on Show FolderShow in FinderOpen Directory. A window with your profile filesfolder will open.
  3. Note: If you are unable to open or use Firefox, follow the instructions in Finding your profile without opening Firefox.

  4. At the top of the Firefox window, click on the Firefox button and then select ExitAt the top of the Firefox window, click on the File menu and then select ExitOn the menu bar, click on the Firefox menu and select Quit FirefoxAt the top of the Firefox window, click on the File menu and select Quit

    Click the menu button New Fx Menu and then click ExitQuit Close 29

  5. Locate and delete the sessionstore.js file and any copies, such as sessionstore-1.js, sessionstore-2.js.

Plugins

Sites that use plugins such as Java, Adobe Reader, or Flash can cause Firefox to hang. For information on troubleshooting plugins and on determining whether a plugin is causing your problem, see the Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems article.

Hang switching tabs

Spybot S&D's "Immunize" feature can add a large number of entries into the Firefox cookie configuration file. This can cause slowdown while switching tabs.

  1. From the menu at the top of the Firefox window, select File and then select the Exit menu item.
  2. Open Spybot S&D.
  3. Click the Immunize icon on the left side of the window.
  4. Right-click in the Immunization list and choose Deselect all from the context menu.
  5. In the Firefox section, put a check mark next to each item.
  6. Click Undo at the top of the window.

Hang after prolonged use

Firefox may hang if left open for long periods of time. To fix the issue, restart Firefox.

If you regularly leave Firefox open so that you return to where you left off, you may want to use Firefox's Session Restore feature. When you exit the program, Firefox can remember your open windows and tabs. When you restart Firefox, you can optionally reload those windows and tabs.

To enable Session Restore:

  1. At the top of the Firefox window, click on the Firefox button and then select Options.At the top of the Firefox window, click on the Tools menu and then 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.

    Click the menu button New Fx Menu and choose Options.Preferences.

  2. Click the General panel (Main panel in Firefox 3.5).
  3. From the When Firefox starts drop-down, select Show my windows and tabs from last time.
  4. Click OK to close the Options window.Click Close to close the Preferences window.Close the Preferences window. Close the about:preferences page.

Firefox is now configured to remember your windows and tabs. You can close Firefox without losing the currently opened web pages, which may prevent Firefox from hanging.


Hang deleting bookmarks folder

Trying to delete a bookmarks folder that contains many bookmarks and multiple levels of sub-folders can cause Firefox to hang. To work around this problem, delete unwanted bookmark sub-folders in small steps. .


Hang at exit

Sometimes when you close Firefox, it may stop responding and remain in memory, even though no Firefox windows are open. This can prevent Firefox from working properly the next time you open it or you may see a "Close Firefox" dialog box with the message, 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.. You must then end all Firefox processes or restart the computer before you can reopen Firefox. (See "Firefox is already running but is not responding" error message - How to fix it for other causes and solutions.)

If Firefox processes that remain in memory at exit are a recurring problem, try these solutions:

  • Sometimes Java applets can cause the Firefox process to persist after exit. Try updating Java to the latest version or, if you don't need the Java plugin, you can disable it from the Plugins panel of the Firefox Add-ons window. For more information, see Use the Java plugin to view interactive content on websites.
  • Using certain Internet security software is reported to cause the issue on some systems:
    • If you use ZoneAlarm on Windows Vista, uninstall it and use another firewall product (or use the Windows Firewall).
    • If you use Avast! Antivirus, switch to another antivirus product if you also have ZoneAlarm installed.
    • If you use Norton 360 2.0, make sure that you have all available Norton updates (for more help, contact Norton Support) and that you have followed the instructions in the Configure Norton 360 to work with Firefox article.
    • If you have upgraded Comodo Internet Security from a version prior to 3.10, the Comodo Safe Surf component from the previous version can cause Firefox to hang at exit. To resolve the issue, you can uninstall Comodo Safe Surf via Windows Control Panel, as its function is now integrated into the current Comodo application.



Based on information from Firefox hangs (mozillaZine KB)