It is possible to load unvetted extensions, but it's inconvenient. If you go to this url in Firefox: about:debugging#/runtime/this-firefox You can install

It is possible to load unvetted extensions, but it's inconvenient. If you go to this url in Firefox: about:debugging#/runtime/this-firefox You can install a "Temporary Add-On", which is any add-on/extension you have stored on your local disk[1]. So you can download an extension from a third party, rename the .xpi to a .zip (Firefox extensions are just zip files with a different extension), unzip it, and use the "Load Temporary Add-on" button to point to the manifest.json file in the unzipped extension. Add-ons installed this way will work as though you installed it via normal means, with the caveat that it will not automatically reload when you restart Firefox, it must be added manually again. I have developed a few extensions, and this is the standard process for testing extensions during development. There is a similar process in Chrome, etc. 1: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Your_first_WebExtension https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/Web...