Last updated: March 7, 2017
Java does not work in Firefox after installing Java
- How to use Java in Firefox (after Firefox 52 NPAPI support removal)
Java is a free software developed by Oracle Corporation, and also a programming language. When you download and install the free Java software, you are installing the Java Runtime Environment (JRE), including the Java Virtual Machine (JVM). When referring to “Java” in this article, we are referring to JRE, which is a web browser plug-in required to run Java applets in your web browser.
If Java does not work in Firefox after installing Java, the very first step in resolving Java-related issues with your computer is to make sure your Java installation is current.
If a plug-in you have installed violates Mozilla’s add-on guidelines, it will be placed on a blocklist. The blocklist exists to disable unsafe add-ons/plug-ins, such as outdated Java versions, from loading. Outdated add-ons/plug-ins could potentially cause harm to your computer. When this occurs, Firefox will block the add-on/plug-in from running, and display the following notification:
Firefox has determined that the following add-ons are known to cause stability or security problems
If this notification displays for you, visit the Firefox Plugin Check. Plugin Check is a free utility that you may use to make sure all of your plug-ins are safe and up-to-date. If Plugin Check determines that any of your plug-ins are out of date, use the utility to update them right away. Once they are updated, re-visit the content that was blocked to see if it displays normally.
In certain cases, you may see the following notification display instead:
Error: A plugin is needed to display this content. Install Plugin
This error notification may display if there is a conflict between Java 7 Update 10 and greater with stand-alone installations of JavaFX. To resolve this issue:
- Uninstall all versions of Java and JavaFX from your computer. You may uninstall Java and JavaFX in the same way you would uninstall any other program — from your Windows Control Panel.
- You may wish to run the Microsoft uninstall utility to repair any potentially corrupted registry keys.
- Restart your computer. Once restarted, launch your web browser (don’t launch any other programs yet).
- Re-install Java on your computer.
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