From MozillaZine Knowledge Base

On Windows systems, Mozilla applications will scan for common plugins at startup, such as Java, Windows Media Player and others, in locations external to the installation directory plugins folder. This article identifies the related preferences that control this behavior and explains how these settings can be modified.

Disabling the plugin scan

Modify these preferences by editing configuration for the user profile. This can be done via about:config, as follows:

• To prevent scanning the Netscape Navigator 4.x directory for plugins, add a new boolean preference named plugin.scan.4xPluginFolder and set the value to "false".

• To prevent scanning the directories specified in the Windows registry for PLIDs, modify the plugin.scan.plid.all preference value from "true" to "false". Plugins in this category include RealPlayer, as well as Flash starting with version 9.0 r45 [1].

• To prevent scanning the Quicktime, SunJRE, WindowsMediaPlayer or Acrobat installation directories, find the related preference and increase the value of the minimum version to a number greater than the version you have installed. For example:
  • To stop the plugin scan for Java plugins, modify the value of the preference plugin.scan.SunJRE from "1.3" to 1.9 [2]
  • To stop the Windows Media Player plugin scan, modify the value of the preference plugin.scan.WindowsMediaPlayer from "7.0" to 19.0 [3].

To return to the default settings, reset the modified preferences via about:config. Note that these changes will effect the current profile and will need to be repeated for any other user profiles.

Related preferences

Plugin scanning is controlled by the preferences listed below, which is presented for information only. Although is possible to stop the plugin scan for for all user profiles by editing the all.js file, as mentioned here this is not recommended, since modifications made to the all.js will be lost at the next program upgrade that replaces the file with a newer version.

Any line preceded by a double slash ("//") is a "comment"; the actual preference lines begin with pref and end with a semi-colon.

In versions since Firefox 0.9 and Mozilla Suite 1.7.a [4] these preference settings are contained in the "all.js" file, located in the "installation directory\greprefs\ subfolder in Firefox (e.g., "C:\Program Files\Mozilla Firefox\greprefs\all.js") and the "GRE\<buildID>\greprefs\ subfolder in Mozilla Suite and SeaMonkey (e.g., "C:\Program Files\Common Files\mozilla.org\GRE\1.8.0.7_2006091003\greprefs\all.js").

// Locate Java by scanning the Sun JRE installation directory with a minimum version
// Note: Does not scan if security.enable_java is not true
pref("plugin.scan.SunJRE", "1.3");

// Locate plugins by scanning the Adobe Acrobat installation directory with a minimum version
pref("plugin.scan.Acrobat", "5.0");

// Locate plugins by scanning the Quicktime installation directory with a minimum version
pref("plugin.scan.Quicktime", "5.0");

// Locate and scan the Window Media Player installation directory for plugins with a minimum version
pref("plugin.scan.WindowsMediaPlayer", "7.0");

// Locate plugins by the directories specified in the Windows registry for PLIDs
// Which is currently HKLM\Software\MozillaPlugins\xxxPLIDxxx\Path
pref("plugin.scan.plid.all", true);

// Controls the scanning of the Navigator 4.x directory for plugins
// When pref is missing, the default is to pickup popular plugins such as
// Flash, Shockwave, Acrobat, and Quicktime. If set to true, ALL plugins
// will be picked up and if set to false the scan will not happen at all
//pref("plugin.scan.4xPluginFolder", false); 

Note that the last preference line listed above is "commented out" by the double slashes ("//"), causing the preference to be missing, which enables the Netscape Navigator 4.x plugin scan.

See also

• Issues related to plugins