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 plugin properly installed and enabled. Starting in Firefox 3.6, Firefox also requires the new Java plugin included in Java 6 Update 10 or above.

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

Warning: There is a recent and widespread security issue where a malicious website can exploit older Java versions (Version 6 update 29 and earlier, also written as 1.6.0_29) to gain control of your computer. Firefox has blocked these versions for your protection. To fix, simply update Java from the official Java website:

Testing Java

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

Enabling Java

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

  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. Click on the Java (TM) Platform pluginJava Embedding Plug-InJava Plug-in 2 for NPAPI Browsers (Mac OS 10.5 & 10.6) or Java Applet Plug-in (Mac OS 10.7)Java plugin to select it.
  4. Click on the Enable button (if the button says Disable, Java is already enabled).
Note: You only need to enable the "Java(TM) Platform" plugin, if it is disabled. The "Java Deployment Toolkit" plugin is used by Java developers to detect your Java version and to deploy their Java applications and does not need to be enabled for Java to work.

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 download the Java installer to your computer.
  4. After the down is complete, close Firefox.
  5. Open the file you downloaded to start the Java installation.

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.

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. 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 the Java(TM) Platform plugin and make sure that it is enabled.
    4. Check if the Java(TM) Platform plugin is correctly detected. All Java plugins listed in the Add-ons window Manager tab should match the version number of the currently installed Java plugin. For example, if Java 6 Update 24 is currently installed, the Java plugin in the Add-ons window Manager tab should be listed as Java(TM) Platform SE 6 U24.
    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 on 32-bit Windows, C:\Program Files (x86)\Mozilla Firefox\plugins on 64-bit Windows
      Java plugin 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.

On Mac OS X 10.6 and below, Java is installed with the operating system. To update Java, use the Mac OS X Software Update feature.

On Mac OS X 10.7, Java is not installed by default. Java for OS X Lion is available from Apple Support Downloads.

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


For Mac OS X 10.5, Apple's Java Update 10 removed support for Java Plugin2, preventing Firefox and other non-Apple browsers from detecting that Java is installed. Mozilla fixed the problem in Firefox 5.0.1 and above so, in order to run Java applets, you should update to the latest version of Firefox.

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)