Use the Java plugin to view interactive content on websites

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Many web pages use Java applets for interactive content such as online games. Java is a programming language that can run on Windows, Mac, Linux, and other computer systems.

  • Java is not the same thing as JavaScript (see this article for information about JavaScript).

Before Firefox can run Java applets you must have the Java Runtime Environment (JRE) properly installed and enabled.

Starting in Firefox 3.6, you also need the new Java plugin included in Java 6 Update 15 and above.

This article will help you install or update Java and get it working in Firefox.

Testing Java

A number of online tools will tell you if Java is installed and enabled in Firefox.

  • You can visit the Java test page at
    • Note: Through the above test, you can also install the appropriate JRE for your system.
  • To verify your installed Java software, see Verify Installation at
  • Java Tester includes links to verify your Java version and whether Java is enabled.

Enabling Java

If Java is not working, make sure that the Java plugin is enabled in the Add-ons window:

  1. Open Firefox.
  2. At the top of the Firefox windowOn the menu bar, open the Tools menu, and click on Add-ons. The Add-ons window will open.
  3. Select the Plugins panel.
  4. Click on the Java item to select it.
  5. Click Enable. (If it says Disable, Java is already enabled.)

Other software that may block Java

Even if Java is installed and enabled in Firefox, it may be blocked by other software or Firefox add-ons, such as the following:

  • The ZoneAlarm Pro software firewall can block Java. For more information on enabling Java through this program, see the ZoneAlarm Pro forum.
  • The NoScript extension for Firefox will block Java. For more information, see the NoScript FAQ

Installing or updating Java

Manual install or update

  1. Go to the download page at
  2. Click the Free Java Download button.
  3. Click the Download Now button to start the online installation.
  4. After the installation is complete, you must restart Firefox.


  • Automatic update: Java for Windows includes a Java Update feature that, in Windows 2000 and later, periodically checks for updates and notifies you when an update is available for installation.
  • Manual update: You can also check for new updates at any time from the Java Control Panel. Open the Windows Start Menu, select Control Panel and double-click Java to open the Java Control Panel, and then choose the Update tab and click Update Now.
Note: To eliminate potential security vulnerabilities and to save disk space, you should remove any older Java versions that may still be installed. For more information, visit


After enabling Java in your operating system and through your Firefox options, Java may still fail to work properly. To activate Java, try the following:

  • Remove outdated Java plugin files from the Firefox plugins folder:
Note: It is recommended that you do not copy Java plugins from other locations to the Firefox plugins folder. Outdated Java plugins can cause Java not to work if you update Java and then uninstall the older Java version, if plugins from the old Java version are still in the Firefox plugins folder.
    1. At the top of the Firefox window, click the Tools menu, and select Add-ons. The Add-ons window will open.
    2. In the Add-ons window, select the Plugins panel, to display a list of installed plugins.
    3. Select each Java plugin listed to make sure that all are enabled.
    4. Check if the Java plugins are correctly detected. All Java plugins listed in the Add-ons window should match the version number of the currently installed JRE. There should be no plugins for earlier versions of Java. For example, if JRE 6.0 Update 22 is currently installed, each Java plugin in the Add-ons window should be listed as Java(TM) Platform SE 6 U22.
    5. If you find Java plugin files listed that do not match your current version, that means that the Firefox plugins folder contains outdated Java plugin files which should be removed. This folder is typically in the following location:
      C:\Program Files\Mozilla Firefox\plugins
      Java files from older versions in the Firefox plugins folder can prevent Java from working. For more information, see the PluginDoc Java FAQ.
  • Add missing registry entry: Sometimes a Windows registry entry that Java needs may be missing. To fix, you should re-install Firefox - see the instructions in How to download and install Firefox on Windows for installation instructions.

Java is a core component of Mac and should be properly installed with the operating system. To update Java, use the Mac OS X Software Update feature.

See Java Plugin Install for Linux at for help installing or updating Java on your Linux system.

Issues or problems related to Java

For more information on specific issues with Java, see Java-related issues.

Additional resources

  • The Java FAQs page at answers some frequently asked questions.
  • PluginDoc includes Java downloads and installation instructions for other operating systems.

Based on information from Java (mozillaZine KB)