Smart Open от Daniel Quinn

Sometimes you don't want Firefox to handle a particular URL and would prefer that it be opened in some other external program. Maybe you'd prefer to delegate the use of certain websites to certain browsers, or maybe you'd just like to bypass the web experience altogether for some sites and load up the content in a video player.

This extension is only half of the solution. You need to install the helper program as well. Full details are available on the project page: https://gitlab.com/danielquinn/smart-open