Issues related to plugins

This article will help you determine if Firefox and Mozilla Suite or SeaMonkey browser problems on Windows systems are related to plugins. If you already know that your issue is related to a specific plugin because of problems with certain web content or because you received an error message identifying the plugin, look through the other articles in the Category:Plugins for a solution.

Before trying these suggestions you should perform the standard diagnostic steps first, to rule out problems caused by other issues such as problematic extensions or other profile issues.

Background

Mozilla browsers often need plugins for web content that cannot be handled internally, such as Java applets, Flash movies and embedded audio and video. (JavaScript is often required for the plugin to run correctly.) Mozilla browsers find installed plugins by searching in different locations [1]. Some common plugins are located via plugin scanning; other plugins are detected in the Mozilla browser installation directory plugins folder, for example, the C:\Program Files\Mozilla Firefox\plugins folder in a typical Firefox install.

Some plugins are known to cause problems or can interfere with other plugins. One way you can diagnose problems you suspect are plugin-related is by removing or disabling the plugin. If the problem goes away, it was caused by the plugin. Keep in mind that if you disable or remove a plugin, embedded web content handled by that plugin will be missing and you may receive a "missing plugin" alert.

Identifying installed plugins

You can see a list of detected plugins by entering about:plugins in the address bar. The installed plugins list will include the file name and a description of the plugin along with the associated MIME types handled by each plugin. All Mozilla browser plugin file names begin with np and end with .dll. (Note that some plugins like Quicktime or Java include multiple plugin files, each with a different file name.) If you set plugin.expose_full_path to "true" in about:config you will be able to see the full path to each plugin file, instead of just the file name, in the about:plugins list.

Mozilla Default Plug-in

Mozilla browser installations include the Mozilla Default Plug-in "npnul32.dll", located in the browser installation directory plugins folder. Mozilla Suite and SeaMonkey need this plugin for the "click here to get the plugin" alert on web pages that need plugins that are missing. Firefox does not require this plugin as the "Additional plugins are required..." yellow message bar will still display without it.

Disabling plugins found in the plugins folder

You can temporarily disable some of the plugins that your Mozilla browser is detecting by renaming or removing the associated files from the installation directory "plugins" folder, as follows:

Firefox

1. Completely exit Firefox.
2. Open the Firefox "plugins" folder, typically C:\Program Files\Mozilla Firefox\plugins.
3. Do one of the following:
   • Rename each "np*.dll" file by adding an "X" before the name, or
   • Remove all the files in the plugins folder to a backup location.
4. Restart Firefox.

If the problem persists, you should check the about:plugins list again to see what plugins are still being detected via plugin scanning. Additionally, some programs that include browser plugins such as Quicktime may copy back any removed plugin files to the browser plugins folder.

If the problem goes away, it was caused by one of the disabled plugins. You can try to identify the problematic plugin and restore the other plugin files or you can simply reinstall any missing plugins as needed.

Mozilla Suite or SeaMonkey

Follow the same procedure given above, except do not rename or remove the Mozilla Default Plug-in "npnul32.dll" from the Mozilla Suite or SeaMonkey installation directory "plugins" folder, since this file is needed for missing plugin alerts (see above).

Disabling the automatic plugin scan

Mozilla browsers will scan for common plugins in other locations, even if the browser plugins folder is empty. You can prevent the automatic scan for for common plugins such as Windows Media Player or Real Player by modifying the related preference settings. For detailed instructions, see this article.

Other methods of disabling plugins

• You can disable Java in your browser settings to prevent Java applets from running. This will help determine whether the Java plugin is causing issues such as a persistent browser process after exiting Firefox, Mozilla Suite or SeaMonkey.
• You can disable the Adobe Reader browser plugin to force .PDF links to open the Adobe Reader program instead of the Adobe Reader plugin, which, if done via the Adobe Reader program preferences, should remove the nppdf32.dll plugin file from all locations (see the Adobe Reader article for additional information).
• You can disable Quicktime plugins for different filetypes via the Quicktime browser settings from within the MIME settings window, by unchecking the file formats you don't want opened by the associated Quicktime plugin. Note that you may have multiple Quicktime plugins depending on how many file types you have enabled in the Quicktime browser settings.
• Firefox only: If you just want to disable the plugin for file download actions, but leave the plugin enabled for embedded files, this can be done via your Firefox options for Download Actions, as explained in this article.

Problematic plugins

The following plugins are known to cause problems in Mozilla browsers. You can disable these plugins by closing your Mozilla browser and removing the associated np*.dll file to a backup location or by renaming the plugin file (to rename the plugin, add an "X" in front of the file name). If the problem goes away, the problem was related to the plugin.

Plugins folder:

• npmozax.dll - The ActiveX plugin will conflict with the the Flash plugin or cause other problems if the wrong version is installed.
• npvlc.dll - The VLC Media Player plugin can cause a conflict with the Windows Media Player plugin and cause problems viewing Windows Media Video files.
• npunagi2.dll - This is the AOL Media Playback Plugin. It launches AOLMediaPlaybackControl.exe to play embedded .MP3 files but doesn't work properly [2].
• npbittorrent.dll - The Bittorrent plugin can cause an empty Download Actions list of file types in Firefox.
• np32dsw.dll- The Shockwave plugin can cause an immediate increase in memory usage. Either uninstall the Shockwave Player, or disable the plugin by removing or renaming the plugin file.
• NPSWF32.dll - The Flash plugin may cause excessive delay or high CPU usage waking the computer from hibernation or standby mode. Note that the Flash plugin may also be located outside the Firefox plugin folder (see below).

Download managers are known to leave behind plugins in the Firefox plugins folder when uninstalled, including:

• npdap.dll - Download Accelerator Plus [3]
• npfd.dll - Fresh Download [4]

If you no longer have the download manager installed and you are experiencing download problems, remove the associated plugin from the Firefox plugins folder. Information about other Download Managers can be found at PluginDoc.

Sometimes outdated versions of plugins that may have been placed in the browser plugins folder may conflict with the currently-installed versions found by scanning the application folder of the program associated with that plugin.

• See Java - Remove outdated Java files from the browser plugins folder
• See Quicktime- Resetting the Quicktime browser plugins

Plugins found in other locations:

• npYState.dll - The Yahoo! Application State plugin file "npYState.dll" can cause problems with Yahoo! Mail. To disable the plugin, open the C:\Program Files\Yahoo!\shared folder and rename the file "npYState.dll" to "XnpYState.dll". Open Firefox and test Yahoo! Mail.

• NPSWF32.dll - The Flash plugin, in some cases, is copied to the C:\Windows\System32\Macromed\Flash folder, so check this location also, even if you've already disabled the Flash plugin by removing or renaming the file "NPSWF32.dll" in the Firefox plugins folder.

See also

• Testing plugins
• Video or audio does not play
• Changing media handling behaviour
• Opening files using plugins