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Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems

Support will end for all NPAPI plugins except for Flash in March 2017, when Firefox version 52 is released. See this compatibility document and this article for details.

Beginning with Firefox version 52, support has ended for all NPAPI plugins except for Adobe Flash. See this compatibility document and this article for details.

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

Note: The 64-bit version of Firefox recognizes and supports only the Adobe Flash and Microsoft Silverlight NPAPI plugins.

Common problems caused by plugins include:

This article describes how to troubleshoot plugins. If you are having a problem with an extension or theme, see Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems. For general information on plugins, see Use plugins to play audio, video, games and more.

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. Click the menu button New Fx Menu and choose Add-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 select Never Activate in its drop-down menu. Repeat this step for each plugin in the list, until all of them are disabled. 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 Always Activate drop-down menu 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 To check if any of your installed plugins are out of date, visit Mozilla's Plugin Check & Updates page.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. Type about:plugins into the address bar and press EnterReturn to display the About Plugins page.
  2. Each entry in the About Plugins page will have "File:" and "Path:", showing the name and location of the plugin file. Use Windows Explorer to navigateNavigate to the folder shown for the plugin you want to remove.
  3. Rename the file to add an X in front of the filename (for instance, 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:

    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 FolderOpen 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. Click the menu button New Fx Menu and then click ExitQuit Close 29 .
  5. Delete the pluginreg.dat file.
  6. Open Firefox
  7. In the Location bar type about:plugins and press EnterReturn to bring up the Firefox plugins list.
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After 6 month searching I found the solution to my problem: Firefox 4.0.1 is hanging on flash ( in youtube for instance ) due to hardware acceleration of the flash display. To turn it off see:

Thank you for reporting a possible solution for problems with the Flash plugin, which is to disable hardware acceleration in the Flash Player settings as documented at

I checked the Firefox hangs or is not responding - How to fix article and it does refer you to the Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems article for problems caused by plugins. Since you have identified Flash as the plugin causing the problem, the next step would have been to research Flash articles. Having a link to Use plugins to play audio, video, games and more might be needed here.

The Flash Plugin - Keep it up to date and troubleshoot problems article has a troubleshooting section that links to Flash videos won't play full screen which has "Disable hardware acceleration" in Flash settings as the solution. I think that the Flash Plugin - Keep it up to date and troubleshoot problems article's troubleshooting section should mention that other performance issues caused by Flash can also be solved by disabling hardware acceleration. I'll copy this to that article's discussion forum.

See /forums/knowledge-base-articles/705012 for related discussion about this article.

This article is one of the top twenty troubleshooting articles but is considered "failing", since its helpfulness rating is less than 50%.

See the related discussion:
/forums/knowledge-base-articles/707113 Focus on troubleshooting

Updating plugins should be the first step - that's easiest.

This was reported in the KB articles forum:

underpass said

Hello, Just by chance I realized that the preference plugin.expose_full_path is not working anymore in Firefox 21. This should be by design (see Bug 661961). So, in Firefox 21 there is no way to get the path of installed plugins and the article Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems should be changed accordingly. Bye

See also:

Plugin file location:
  • Mozilla 20 and below: To show the full path to the plugin instead of just the file name (e.g., in Firefox 20), type about:config in the address bar and press the Enter key. Find the preference plugin.expose_full_path and set it to true (double-clicking the preference name will toggle the setting). Caution: Exposing the plugin location may have security implications on some systems. It's best to reset the preference to the default "false" value when you are done. ref.
  • Mozilla 21: There is no way to display the full file path in the about:plugins list. An alternate way to find the plugin file location (e.g., in Firefox 21) is to inspect the contents of the "pluginreg.dat" file, located in the profile folder for your Mozilla application.
  • Mozilla 22 and above: Starting in version 22 (e.g., Firefox 22) an extra row "Path:" is included in the about:plugins list, which displays the full file path for all plugins. (bug 661961).

Related discussion in the Use plugins to play audio, video, games and more article: [Fx42] Add a note for users who install Windows 64-bit Firefox that only the Flash plugin works

Related bug: Bug 1225293 - Support Silverlight for Win64 Firefox ....which is linked from Bug 1187005 - Some plugins (Silverlight, Lync Web App, Java, ...) are not recognized as installed with Firefox 64-bit build on Win64 (comment 165) Quote:

Chris Peterson [:cpeterson] 2015-11-24 09:59:21 PST

64-bit Silverlight will be re-enabled in Firefox 44 by bug 1225293. \o/

I also have edits pending to the Use plugins to play audio, video, games and more and Use the Silverlight plugin to play audio and video articles.

The fix for Bug 1225293 - Support Silverlight for Win64 Firefox - was uplifted to Firefox 43 and Firefox 44 so I'm editing the warning.

bug 1187005 comment 167

Chris Peterson [:cpeterson] 2015-12-02 10:02:09 PST

(In reply to Alice Wyman from comment #166) > Chris, can you confirm whether this will take place in the Firefox 43 > release?

Yes, 64-bit Silverlight is now enabled in Firefox 43.

One caveat: at the moment, Amazon Video won't play because it still thinks 64-bit Firefox does not support Silverlight. But if you use an extension to change your User-Agent to look like 32-bit Firefox, then Amazon Video will play. I have asked Amazon to unblock 64-bit Firefox.