FOSS Post - https://fosspost.org/tutorials/prepare-for-firefox-57-with-these-10-web-extensions
Mozilla Firefox browser is moving to “web extensions” and is dropping support for the legacy XPCOM & XUL add-ons. This means that every single add-on you have on your browser won’t work with Firefox +57 unless it was rewritten using this new technology.
This is bad news for a lot of us. Thousands of add-ons won’t be used anymore because of this. A lot of developers do not plan to invest more time in porting their add-ons into the new technology. However, things have to move on. Mozilla’s point of view is that it’s time to drop this legacy technology