Firefox hangs or is not responding - How to fix

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  • Creator: NoahSUMO
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When Firefox hangs, it stops responding to your clicks and keystrokes and doesn't seem to be doing anything. Also, a "(Not Responding)" label is displayed in the title bar and the mouse cursor becomes a spinning wheelhourglass when it's over the Firefox window.Also, the mouse becomes a spinning wait cursor when it's over the Firefox window. This article gives you solutions to Firefox hangs depending on when they happen.

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.

Note: The Refresh Firefox feature can fix many issues by restoring Firefox to its default state while saving your essential information. Consider using it before going through a lengthy troubleshooting process.
Note: If you send performance data, Mozilla will gather data including hangs for your Firefox, which will help making Firefox better for future versions.

Firefox hangs at random times

If Firefox seems to hang randomly and not after a specific action (for example, downloading a file or quitting Firefox), try the solutions in this section.

Create a new places database

If hangs are periodic, it may be caused by a corrupted places database.

Information: The "places" files store the annotations, bookmarks, favorite icons, input history, keywords, and browsing history (a record of visited pages).

To create a new places database, do the following:

Warning: This will clear your browsing history and remove bookmarks of the day.
  1. The template "ProfileFolder" does not exist or has no approved revision.
  2. Click the Firefox menu Fx89menuButton and select Exit.Click the Firefox menu at the top of the screen and select Quit Firefox.Click the Firefox menu Fx89menuButton and select Quit. Wait until Firefox has completely quit.
  3. In the Firefox profile folder, find and rename the files places.sqlite to places.sqlite.old and places.sqlite-journal to places.sqlite-journal.old (if it exists).
    • To rename a file, right-click on it and select rename from the menuclick on it once to select it and then click a second time on the file name to make it editable. Then add .old to the end of its name.
  4. Finally, reopen Firefox.
    • When Firefox reopens it will create a new places database. Your browsing history will be lost but Firefox will automatically import your bookmarks from the most recent backup file.

Turn off hardware acceleration

With some graphics card and graphics driver setups, Firefox may hang when using hardware acceleration. You can try turning off hardware acceleration to see if it fixes the problem.

  1. In the Menu bar at the top of the screen, click Firefox and then select Preferences or Settings, depending on your macOS version.Click the menu button Fx89menuButton and select Settings.
  2. Select the Advanced panel and the General tab.
  3. Uncheck Use hardware acceleration when available.
  4. Click the Firefox menu Fx89menuButton and select Exit.Click the Firefox menu at the top of the screen and select Quit Firefox.Click the Firefox menu Fx89menuButton and select Quit.
  5. Start Firefox the way you normally do.

If the problem is no longer happening, then hardware acceleration was likely the cause. You can try updating your graphics drivers to see if that fixes it or simply run without hardware acceleration.

Troubleshoot your 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.

Delete duplicated Session Restore files

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

  1. Open your profile folder:

    • Click the menu button Fx89menuButton, click Help and select More Troubleshooting Information.From the Help menu, select More Troubleshooting Information. The Troubleshooting Information tab will open.
    • Under the Application Basics section next to Profile FolderDirectory, click Open FolderShow in FinderOpen Directory. A window will open that contains your profile folder.Your profile folder will open.
    Note: If you are unable to open or use Firefox, follow the instructions in Finding your profile without opening Firefox.

  2. Click the Firefox menu Fx89menuButton and select Exit.Click the Firefox menu at the top of the screen and select Quit Firefox.Click the Firefox menu Fx89menuButton and select Quit.
  3. Locate and delete the sessionstore.js file and any copies, such as sessionstore-1.js, sessionstore-2.js.

Change the PAC implementation

If you're using a proxy auto-config 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. In the Menu bar at the top of the screen, click Firefox and then select Preferences or Settings, depending on your macOS version.Click the menu button Fx89menuButton and select Settings.
  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 workaround to your network administrator.
  6. Click Cancel.

Firefox hangs while playing Flash videos

See Playing Flash videos makes Firefox hang.

Firefox hangs after using it for a long time

Update Firefox

The latest Firefox versions includes improvements in memory usage, especially during long sessions. Update Firefox to the latest version.

Restart Firefox

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. For more information, see Configuring session restore.

Firefox hangs while loading the first window

Speed up Session Restore

If you have many tabs to restore, Firefox may hang while loading those sites. Make sure that Don't load tabs until selected is checked in the Tabs panel of the OptionsPreferences window so that only the last selected tab is loaded at startup. You can also try to use Tab Groups so that only websites in the visible tab group load first.

Firefox hangs when 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 window, click on the Firefox button (Tools menu in Windows XP), and then click DownloadsOn the menu bar, click on the Tools menu, and then click DownloadsAt the top of the Firefox window, click on the Tools menu, and then click Downloads. The Downloads window will open.Click the Downloads button fx20 download icon and then click Show All Downloads. The Library window will open.
  2. Click Clear List. The download history is cleared.Click Clear Downloads to delete the download history.
  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. In the Menu bar at the top of the screen, click Firefox and then select Preferences or Settings, depending on your macOS version.Click the menu button Fx89menuButton and select Settings.
  2. Select the General panel.
  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. Close the Settings page. Any changes you've made will automatically be saved.

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.

Disable virus scan in Firefox preferences

With some antivirus programs, the virus scan that Firefox starts after files are downloaded may cause Firefox to hang. You can disable virus scanning with the following steps (this will not disable your antivirus program):

  1. Type about:config in the address bar and press EnterReturn.
    A warning page may appear. Click Accept the Risk and Continue to go to the about:config page.
  2. Locate the browser.download.manager.scanWhenDone preference and double click it to change the value to false.

Firefox hangs when you quit it

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 an error message, Firefox is already running, but is not responding.A copy of Firefox is already open. 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 - How to fix for other causes and solutions).

Close Firefox completely

  1. Click the Firefox menu Fx89menuButton and select Exit.Click the Firefox menu at the top of the screen and select Quit Firefox.Click the Firefox menu Fx89menuButton and select Quit.
  2. Close any remaining dialog boxes or secondary windows such as the Downloads window.


If Firefox processes that remain in memory at exit are a recurring problem, try the following solutions.

Troubleshoot your extensions

A problematic extension can cause the problem, which can be resolved by disabling or uninstalling the extension. For information on diagnosing and fixing problems caused by faulty extensions, see the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article.

Update or disable the Java plugin

Sometimes Java applets can cause the Firefox process to persist after exit. Try updating Java to the latest version by going to Mozilla's plugin check page or, if you don't need the Java plugin, you can disable it from the Plugins panel of the Firefox Add-ons Manager. For more information, see Use the Java plugin to view interactive content on websites.

Troubleshoot your Internet security software

Interactions between certain Internet security software (firewall, anti-virus software) is reported to cause hangs on some systems. You can try to configure your firewall to see if it helps the hang go away.

Firefox hangs when Windows resumes from hibernation on Thinkpad

When resuming Windows from hibernation and Firefox hangs for several minutes it might be due to an issue of the pre-installed "ThinkVantage Technologies Power Manager 6". One option to solve this is to uninstall the software. Another option is to check for a later version of the software on the Lenovo support website and see if that fixes the problem. See Bug 1106202 for more details.




Based on information from Firefox hangs (mozillaZine KB)