Firefox 57 is set to bring the biggest shake-up that Mozilla's browser ecosystem has seen in quite some time, and the simple reason is that a huge number of browser extensions and add-ons are set to stop working.
This is far from a surprise, with the switch from XUL to WebExtensions first signalled in mid-2015, but it is a hard break with the past.
Many popular extensions have already been ported to the new framework, but due to extra restrictions imposed by WebExtensions, some existing add-ons are simply unable to do what they once did.
For those still using Firefox 56 and earlier who would like to know what they are going to lose when they upgrade to 57, you are able to see what will disappear thanks to the Add-on Compatibility Reporter.
After installing the add-on, head over to the about:addons page in your browser, and any extensions with a bright yellow Legacy label are sitting on death row.
Ironically, the Add-on Compatibility Reporter is among the extensions that will stop working when Firefox is updated to Quantum.
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How to deal with add-ons that will not work is something each user will need to investigate, but Mozilla has said most users should not be impacted by the shift to Quantum.
For users who absolutely have to keep using a XUL-based extension, it is possible that using a fork of Firefox dubbed Pale Moon could work, or switching to Firefox's extended support release will get another 11 months on Firefox 52, or sitting on Firefox 56 for as long as is needed.