: For developers or testing, you can load it temporarily by navigating to about:debugging , clicking This Firefox , and selecting Load Temporary Add-on MDN Web Docs
: According to Mozilla Support , you can install these files by opening the Add-ons Manager in Firefox, clicking the gear icon, and selecting "Install Add-on from file..." . leethax net firefox extension new
Find and install add-ons to add features to Firefox - Mozilla Support : For developers or testing, you can load