Change a pref in the advanced configuration of Firefox: # Enter '''about:config''' in the address bar # Accept the warning # Enter ''plugin.default'' in the search box, you should get 2 lines # For both lines, double-click on the value and change it (respectively 1 and 2 by default) to '''0'''. *0 - all plugins are "never activate" *1 - all plugins are "ask to activate" *2 - all plugins are "always activate" Note it will not change the pref for a few plugins: Flash, Java, codec H264… If you want also to disable the few plugins mentioned above, enter '''plugin.state''' in the search box of about:config, find lines ending with '''flash''' and '''java''' and change their values to 0 (by default, 2 for flash and 1 for java). On websites requiring one of these plugins, you will have to click on a button at the top left to show the activation popup.