You cannot run the Java NPAPI Plugin from Oracle in Firefox 58.0.2 Why do Java, Silverlight, Adobe Acrobat and other plugins no longer work? -https://support.mozilla.org/en-US/kb/npapi-plugins You need to use Firefox 52 ESR (32-bit version on Windows) as Fx 53.0 and later only allows the Flash Player to run. https://www.mozilla.org/firefox/organizations/all/ or the more self contained https://portableapps.com/apps/internet/firefox-portable-esr https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles http://kb.mozillazine.org/Shortcut_to_a_specific_profile You should use the ProfileManager to create and use a separate Profile from any Profile you use with current Releases like Fx 58.0.2 as it should not be shared. Use Java 8 as Oracle dropped the Java Plugin in Java 9. https://java.com/en/download Chrome, Chromium and Opera dropped support of NPAPI Plugins (which includes Java) since Sept 2015.