When you access a webpage that runs a Java applet, it will ask you whether you want to run this application.You can tell you've got the right version by clicking Help and then About Firefox. You can either overwrite your old Firefox or create a new directory with a different name to preserve your old Firefox. During the installation you'll be asked for the directory in which to install Firefox ESR.

Scroll down to your favorite language, and click download in the appropriate column.If in Linux, you should probably choose the first Linux column (not Linux 64-bit). Download firefox-esr-l10n-sr102.9.b for Debian Sid from Debian Main repository. If you are using Firefox in macOS, choose that column.Only the first version (32-bit) supports Java. Do NOT choose from the second column (labeled 'Windows 64-bit'), even if you have a 64-bit computer. Version 102.8.0 for Windows 圆4, English 59MB download / 209MB installed. If you are using Firefox in Windows, you'll choose from the first column (labeled 'Windows'). Note that there are five download columns.Amongst the latest features is removal of support for Java. The page will advise you that Firefox ESR is for organizations, while individuals who want the latest features should use normal Firefox.If you want further advice on how to install Firefox ESR, try this. You can't have both running at the same time, without some effort (and some risk). You can install it on your machine (as described below) and then use it as your standard version of Firefox or you can keep the current personal version of Firefox (currently version 55) and run one or the other as you like. Firefox ESR (Extended Support Release) version 52, 32-bit, is a version of Firefox that supports Java applets.

Firefox 52 esr download