Firefox 57 is both an exciting and scary prospect for me: user feedback of Firefox Nightly suggests that Mozilla has largely eliminated the browser’s sluggishness, yet there is huge tradeoff in that practically none of my current 15-something add-ons will continue to function. It is estimated that only 20% of all Firefox add-ons are WebExtensions-ready. ...Mozilla said it will continue to allow developers to upload and list legacy Firefox add-ons on its add-ons portal (AMO), but they'll only show up for users with older browsers and buried in search results under newer WebExtensions-compatible add-ons. Changes are already being rolled out to AMO and Firefox 57 (currently Firefox's Nightly edition). The release of Firefox 57 is the end of a two-year-long project that started in August 2015 when Mozilla announced the new WebExtensions API that would eventually replace the older Add-Ons SDK.