How to Check Which Firefox Extensions Will Stop Working in Firefox 57

Ben Stegner 18-09-2017

Firefox has long been the browser for power users Firefox Freedom! Four Things Chrome Doesn’t Let Users Do Think Chrome can do everything? Think again. Here are four things Firefox users can do easily that Chrome users basically can't. Read More , thanks in no small part to its vast extension library 7 Extensions Firefox Users Love That No Other Browser Has Extensions aren't always supported across all browsers. Check out these beloved Firefox-only extensions that are so useful that you may be swayed over from whichever other browser you currently use. Read More . These powerful addons let creative developers tweak the browser in awesome ways, but that kind of power also exposes Firefox to problems.


For a long time, Firefox’s addon system meant that a bad extension could cause issues in your browser, or even be malware posing as helpful.

To remedy this, the upcoming Firefox 57 is making a big switch. From that version on, Firefox will use addons that are similar to what Chrome uses — they can’t modify the browser’s code, so they pose less of a threat.

Old extensions will be called Legacy and won’t be supported come Firefox 57. You should check right now to see which of your extensions are headed to extinction so you can plan ahead.

First, make sure your browser is up-to-date by clicking the three-bar Menu icon in the upper-right of Firefox. Click the Help icon, then About Firefox to check for updates. You must have Firefox 55 or above for the browser to alert you to legacy extensions.


Once that’s done, visit Menu > Add-ons and make sure the Extensions tab is highlighted on the left side. Any extensions that say LEGACY after them don’t conform to the new standard. Mozilla has stated that as November approaches, it will suggest “suitable replacements” for addons that don’t see updates.

But you can get a head start on that now.

How to Check Which Firefox Extensions Will Stop Working in Firefox 57 Firefox Legacy Extensions

Check out the Are we WebExtensions yet? page for information on whether the developers of your favorite extensions are working on updating them.

If you need an alternative for one that’s not making the switch, check out this Google Sheet that the Firefox Reddit community has put together. It lists the status of addon ports and provides alternatives where possible.

Hopefully this won’t affect your use of Firefox too much. Most major extension providers should have no problem modernizing their offerings, while extensions that haven’t seen updates in a while will probably break permanently after this change. But in the long run, it will make Firefox stabler and safer.

Can’t live without your favorite extension? Why not give Opera a try instead I Switched From Chrome to Opera and I’m Never Going Back Any browser works. There's only one reason to pick one over another: it's more in line with how you like to browse the web. And you might prefer Opera, too. Read More ?

How many Firefox extensions do you have installed right now, and how many of them are legacy addons? Do you have alternatives lined up for them? Tell us how this change will affect you in the comments!

Image Credit: MariMarkina/Depositphotos

Related topics: Browser Extensions, Mozilla Firefox.

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  1. marni
    October 3, 2017 at 2:52 am

    Mozilla will "suggest suitable replacements for (broken) extensions"? Hey Mozilla i was just thinking the same thing.
    Nice knowing you- see you around.... not.

  2. Tim Dawson
    September 20, 2017 at 8:47 am

    All except one of my seventeen extensions in DevFox died this morning with no warning at all (because I don't spend my time visiting pages like this). I'm not happy. Unless my favourite extensions get updated I shall have to look elsewhere, which will be a shame after more than a decade with Firefox.

  3. Frank Thomas
    September 18, 2017 at 6:30 pm

    Firefox is Windows in disguise… Spend time setting things up they way they want, then after a lot of time eradicate a lot of work by a change. Opera or even Safari seems better not.

  4. Andysnat
    September 18, 2017 at 4:14 pm

    If I cant get FF to run how I like after the change, i.e. if current extensions stop working, and it looks like many will, I shall have to move away to somewhere the same effect can be had. At the moment, that'll be Chrome. A great shame.

  5. Will
    September 18, 2017 at 2:42 pm

    6 of my eight extensions are showing as "Legacy". Firefox used to be my full-time browser. Now it's my part-time. It's about to get completely deleted.

    • Ben Stegner
      September 18, 2017 at 2:50 pm

      I wouldn't fret yet. Many developers are working on porting their extensions to the new standard and might not complete this until closer to November.

      There's a good chance not all of them will make the jump though. In that case, I don't blame you for jumping ship. I've had trouble getting excited about anything Firefox does in years myself.