The 64-bit version of Firefox does not support NPAPI plug-ins, including Java.
Beginning with Firefox 52 (released March 2017), plug-in support is limited to Adobe Flash, and drops support for NPAPI, impacting plugins for Java, Silverlight, and other similar NPAPI based plugins.
If you have problems accessing Java applications using Firefox, Oracle recommends using Internet Explorer (Windows) or Safari (Mac OS X) instead. Developers and System administrators looking for alternative ways to support Firefox users should see this blog regarding Launching Web Start applications.
Mozilla offers an Extended Support Release (ESR) version of Firefox specifically for use by organizations who need extended support for mass deployments. Only Mozilla Firefox 52 ESR 32-bit release will continue offering support for the standards-based plugin support technology required to launch Java Applets. To see if you are using an ESR release, check the Firefox menu item (Help -> About) and looking for the "ESR" identifier.
Mozilla maintains Firefox ESR Releases for approximately one year. Developers and users still relying on the Java plugin technology in the 32-bit Mozilla Firefox web browser should consider migrating to a different solution.
NOTE: The workaround applies to Firefox 42, and requires Windows Java Version 8 Update 66 Build 18 or later versions. » See JDK-8133523 for related information.
A few options are listed. The simplest method is noted first and recommended. Other available options are not recommended for non-technical users.
dom.ipc.plugins.java.enabledin Firefox preferences
about:configin the address bar
Instructions are based on Mozilla references listed below.
Older versions of the Java Deployment Toolkit (DT) and the Java Plugin have been disabled by Firefox. Some Java versions are flagged by Firefox as 'Add-ons may be causing problems'.
If Firefox thinks an add-on is unsafe and can cause a security risk, it will block it from loading. In case of a soft block Firefox will present a warning message but will allow the user to continue if they wish but with compromised security. In the case of a hard block Firefox will block installation so that the user cannot use this add-on. To resolve this, the user should update to latest version of Java.
Upgrading to the latest Java version should resolve the issue. If you see the warning message, follow these steps:
This could be due to a conflict that Java versions 7u10 and above have with stand alone installations of JavaFX. Example: If Java 7u5 and JavaFX 2.1.1 are installed and if Java is updated, Firefox is unable to detect that the newly installed Java.
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