By default, Firefox allows Java applets to be executed through your browser. However, you may decide that you do not wish for them to automatically launch in your browser.

To disable Java applets:

1. At the top of the Firefox windowOn the menu bar, open the Tools menu, and click on Add-ons. The Add-ons window will open.
2. Select the Plugins panel.
3. Select Java.
4. Click Disable.
   
   
   
   
   
   

Java applets will no longer be permitted to launch in Firefox.