Firefox 56: Last Stop before Quantum

Here at Mozilla, we’re extremely excited about next month’s release of Firefox Quantum (preview it today in Developer Edition!) which brings massive speed improvements, a brand new UI, and several new or improved Developer Tools.

But that’s next month. What about last week’s release of Firefox 56?

Browser Features

For users, Firefox 56 sports two major changes:

First, Firefox Screenshots is a brand new, built-in tool for capturing and (optionally) sharing images of web pages. The tool makes it easy to select regions of the page based on the underlying DOM structure, though both full-page and free-form screenshots are also available.

graphical image of a Firefox Screenshot

Of course, the Developer Tools retain their own screenshot capabilities. For example, you can right-click on any node in the Inspector to capture a screenshot of that node, or you can use the screenshot command in the Developer Toolbar.

Second, Firefox is now 64-bit by default on all operating systems, and existing 32-bit installations will automatically upgrade to 64-bit builds if supported by the underlying hardware.

What’s New for Developers

For developers, Firefox now supports “headless” mode on all operating systems, which makes it possible to run Firefox without actually displaying a window on the screen. This is remarkably useful for automated testing, both during local development and as part of a continuous integration (CI) pipeline.


We’ve also put an enormous amount of effort into Firefox’s Developer Tools. You can read all about the current and upcoming features in Julian Descottes’s article, but we’re especially proud of our completely new debugger: as part of the “devtools.html” project, we completely rewrote the debugger as a modern web application, powered by React / Redux, and using standard HTML, JavaScript, and CSS.

You can find the source code for the debugger on GitHub.

Bidding Farewell to Legacy Add-Ons

Finally, Firefox 56 is the last release to support legacy APIs for add-ons. In their place we’ve created “WebExtensions,” a set of cross-browser extension APIs that we hope to standardize at the W3C. Since many WebExtension APIs are compatible with Chrome, Edge, and Opera, popular add-ons from other browsers (like the Vue.js DevTools) can run on Firefox without significant modification.

Unfortunately, the impending removal of old APIs with next month’s general release of Firefox Quantum will necessarily end support for several legacy add-ons. For example, the new APIs do not offer the degree of UI modification necessary to support Classic Theme Restorer. However, nearly 5,000 add-ons are already available using the new APIs, including Tree Style Tab, Tab Center Redux, and uBlock Origin. The APIs themselves are also still being developed and expanded, so expect to see greater capabilities with each release of Firefox.

In most cases, the upgrade to Firefox Quantum will be painless. Most popular add-ons will update to the new APIs before the release of Firefox Quantum, and Firefox will suggest replacements inside about:addons for those that don’t.

If you’ve ever built a Chrome extension, consider porting it from Chrome with the help of our and <a href="">web-ext</a> tools. In most cases your Chrome browser extension will run in Firefox or Microsoft Edge with just a few changes. Let us know how it goes. If you have ideas or questions, you can contact the team on the dev-addons mailing list or #extdev on IRC.

About Dan Callahan

Engineer with Mozilla Developer Relations, former Mozilla Persona developer.

More articles by Dan Callahan…


  1. jxn

    I’m not able to reach without www (clicking the link failed). Is there a problem with that site at the domain apex? It dooesn’t look like it’s pointed to the same heroku app.

    October 4th, 2017 at 09:36

    1. Dan Callahan

      Whoops! Updated the URL, will file a bug to get the DNS updated.

      October 4th, 2017 at 09:54

      1. Melchior

        I am REALLY disappointed with Mozilla…
        I have been using Firefox since v2.0 so very long ago..
        the XUL/XPCOM extension system is WHAT SETS FIREFOX APART FROM ALL THE REST as the BEST…

        I rely on
        I AM am running 20 Firefox extensions…
        [Legacy Extensions] = 12 <– MOST of which cannot be moved to Web Ext.
        [Web Extensions] = 8

        [Legacy] about:addons-memory 2016 10.0.1
        [Legacy] Add-ons Manager – Version Number 1.5
        [Legacy] Add-ons Manager Context Menu
        [Legacy] Classic Theme Restorer 1.7.2beta1
        [Legacy] Download Manager Tweak 1.0.12
        [Web Ext.] Easy YouTube Video Downloader Express 10.5
        [Web Ext.] Google search link fix 1.6.5
        [Legacy] Mozilla Archive Format 5.0b3
        [Web Ext.] Secure Login (Embedded WebExtension) 0.2.1<– WILL be W.E. when they remove the Legacy CODE..
        [Web Ext.] Secure Password Generator 1.0.6
        [Web Ext.] Stylus
        [Legacy] Tab Mix Plus
        [Web Ext.] uBlock Origin 1.14.11_rc14 (FF/WF v52 or NEWER ONLY)
        [Legacy] UnMHT 8.3.2

        DISABLED most of the time:
        [Legacy] About Sync extension for Firefox 0.0.14
        [Legacy] Add-on Compatibility Reporter 2.2.4
        [Web Ext.] Elite Download Manager 0.1.0
        [Web Ext.] GitHub Notifier 1.1.0
        [Legacy] Greasemonkey 3.17<– WILL be W.E. when they remove the Legacy CODE..
        [Legacy] Tab Memory Usage 0.2.7

        while Web Extensions are new and all… they are still too young..
        and quite frankly. Web. Ext. are INFERIOR to to the XUL extensions…
        XUL is Firefox's greatest FEATURE!!

        quite frankly Mozilla is THROWING its entire advanced USERBASE under the bus as it were…

        October 12th, 2017 at 10:34

  2. Camden Narzt

    Ugh FF57 is so bad for my workflow.

    link location bar broken
    websocket monitor broken
    tab groups broken

    And after sacrificing all the extensions that make Firefox worthwhile it only hits 60% of Safari’s speed. I might as well just go there since none of my extensions are going to work either way.

    October 4th, 2017 at 10:45

    1. Dan Callahan

      Terribly sorry for your experience. We should get websocket monitoring back in a few releases, follow Bug 885508 to track its progress. Similarly, Tab Groups depends on Bug 1384515.

      Can you tell me more about your problems with the link location bar?

      I’d suggest looking into Firefox ESR if your add-ons are absolutely critical to your work. Using ESR will allow you to receive security updates while still keeping your legacy add-ons for the first few releases of Firefox Quantum. You won’t get new features (ESR is based on an older version of Firefox), but by the time ESR upgrades to Quantum, you should be able to go back to the regular channel with an expanded set of WebExtension APIs.

      Speed benchmarks can be misleading; much of the work in Firefox Quantum went into improving performance with many tabs open, and to improving perceived performance. Even when we don’t win on a single-tab benchmark, we may still offer an experience that feels better.

      October 4th, 2017 at 21:41

      1. Camden Narzt

        Thanks for the links.

        A link location bar API isn’t going to be provided because it would require work to be put into it, see this bug for discussion:

        In my experience with FF57 on the dev-edition channel, FF57 feels much slower than FF56. It takes a couple seconds longer to get to first paint and about a second longer for the page to be finished loading. So I’m not convinced that the benchmarks are off in this case.

        Now, I’m not in the common cohort when it comes to performance, as I use a fairly powerful computer and have a fast internet connection; so perhaps the developers have optimized too much for constrained systems but the end result is that FF57 feels slower to me.

        October 5th, 2017 at 10:34

      2. Marcin W. Dąbrowski

        > I’d suggest looking into Firefox ESR

        Is it possible to migrate back the FF56 profile into ESR? Will you provide some kind of tool helping in that migration, after splitting places.sqlite?

        October 6th, 2017 at 10:24

  3. Dumindu

    Please add new APIs to support Tab Mix Plus and Tab Groups. We can not replace them with Tab Center Redux.

    Suggesting Tab Center Redux for Tab Groups is a joke, seriously!

    October 4th, 2017 at 11:35

    1. Dan Callahan

      We’re working on it. Bug 1384515 makes tab groups possible, while Bug 1226546 keeps track of things we need for Tab Mix Plus.

      Tab Center Redux is a great add-on on its own merit; it’s not intended to replace Tab Mix Plus.

      October 4th, 2017 at 21:33

      1. Albert

        The “replacements suggestion” feature also pointed me to “Tab Center Redux” the other day as a possible alternative for “Tab Groups”. It didn’t make any sense to me either. Not sure which team is looking after the plugin store, but I would recommend to only explicitly suggest an alternative if that caters for at least the main functionality of the add-on it is meant to replace. I understand that (we) the users of “Tab Groups” are a noisy minority, a minority nevertheless.
        Fingers crossed Conex will get the APIs it needs in time, as this looks like a promising alternative :)

        Looking forward to many new and interesting (and high-performance) add-ons!

        Love the new debugger, and screenshots is already one of my go-to tools.

        October 6th, 2017 at 18:45

  4. Dmitry

    > Firefox Quantum will necessarily end support for several legacy add-ons

    That’s a bit disingenious. Thousands of addons will cease to work (IIUC there are more of them than of those that had been ported to WE).

    It might be a necessary sacrifice, but let’s not downplay it too much.

    October 4th, 2017 at 14:30

    1. Dan Callahan

      I may be over-correcting after reading one too many catastrophic predictions.

      At one end of the spectrum, it’s technically true that the move to WebExtensions literally breaks every existing add-on. However, most mainstream add-ons already have Chrome versions that can serve as drop-in replacements on Firefox, or they separate common functionality from browser-specific integration code, which reduces the cost of porting. Even add-ons that have to be redeveloped from scratch, like Tree Style Tab, end up working out.

      UI customization APIs are still limited, and gestures are an obvious gap, but we’ll get there. Otherwise, the top add-ons should all either finish their port by November or there will be replacements waiting.

      October 4th, 2017 at 21:29

      1. xn7

        Wouldn’t it be better to first “get there” and then drop support for “legacy” extensions? As others have pointed out, Firefox 57 will likely break many people’s workflow and despite the voluntary efforts of many addon developers, it is not possible to provide drop-in replacements with the limited APIs currently available. And even if addons “finish their port” there needs to be more time for testing and bug fixing before releasing them for the majority of users. This kind of “last-minute port” is unlikely to lead to a very pleasant user experience.

        It would be really helpful if Firefox 56 could be made an ESR and continue to get support for at least another year, or even better 2 – 3 years, until the new API is feature-complete, stable and tested. I really can not understand the rush here.

        October 4th, 2017 at 23:40

        1. Dan Callahan

          Based on telemetry, we’re confident that we’re already there for the vast, overwhelming majority of Firefox users. That’s not comforting if you depend on an add-on that doesn’t have a replacement, but we’re not going into this blindly: we covered enough APIs and saw enough adoption the we felt comfortable flipping the switch.

          October 7th, 2017 at 11:43

  5. njn

    “existing 32-bit installations will automatically upgrade to 64-bit builds if supported by the underlying hardware.”

    I’ve been told that 1% of eligible users will be upgraded this week. If that goes well, the remaining users will be upgraded at a rate that is still to be determined.

    October 4th, 2017 at 21:10

  6. Álvaro González

    All the add-ons I have will stop working in Firefox/57 except one (a screen-shot utility I no longer need anyway because the feature is builtin now).

    The sad thing is that all these extensions have not been updated in years and are basically abandoned. This is going to be a painful but probably necessary clean-up. When it comes to add-ons, I don’t need a huge abandonware repo. I prefer quality over quantity.

    October 5th, 2017 at 01:07

    1. Dan Callahan

      What specific add-ons are you using that are most important to you?

      October 7th, 2017 at 11:45

      1. Álvaro González

        The ones I’ll be missing most are:

        – CSS Reloader
        – Add Bookmark here 2 (already missing it, it doesn’t work in FF/56)
        – LastPass (this is a commercial tool so I presume they’ll eventually upgrade it)

        Less important, but also useful:

        – Dictionary Switcher (it never worked as advertised anyway)
        – Saved password editor (I believe it’s just a short-cut for a builtin dialog)
        – Web Developer

        The others are pretty secondary.

        October 12th, 2017 at 01:01

      2. Álvaro González

        I forgot to mention that I sometimes make heavy use of extensions to take screen-shots and paste them into a word processor. Apparently, the new API no longer allows to implement the “Copy to clipboard” feature and it’s pretty inconvenient.

        October 12th, 2017 at 01:05

  7. Kinne

    I have no idea why software developers have such a fetish for making their product uglier with every update, but I will NOT be using quantum if it’s impossible to make an addon like classic theme restorer to fix your hideous UI. Seriously, you had a great UI a few years ago, but you just keep making it worse with every update. Why couldn’t you just leave it alone? Ever heard the phrase “if it ain’t broke, don’t fix it”? At the very least, you NEED to include an option to use old UI versions in the settings. I’ve been a loyal firefox user since 2008, but every time you change the UI, chrome gets more appealing. At this rate, even IE will be a better choice than the uglier-every-month firefox.

    October 5th, 2017 at 01:11

    1. Mark

      For better or worse, design styles go through phases. Right now we’re in the ugly “Flat Design” style, but we’ll pull out of it eventually. After all, we survived the ’70s, didn’t we? ;-)

      October 6th, 2017 at 08:05

  8. Mr. Clean

    Quantum is AWESOME just add one last thing – when we type youtube in address bar and press tab it should search in youtube like in previous versions.
    Keep up the good work.

    October 5th, 2017 at 08:08

  9. Prashant

    I have started getting a pop up on my FF56 that my “Tile Tabs” will no longer work in FF57 and that I should use “Tile Tabs WE”. I just went and checked for that extension in Chrome. Instead of splitting the browser window, it’s creating two browser windows and placing them side by side. That’s so bad. I can do that manually also. That’s disappointing.

    October 5th, 2017 at 11:56

    1. Catmato

      According to the developer of Tile Tabs:

      “There have been contacts with Mozilla about providing an interface that will support an a new add-on that will work much more like the original Tile Tabs, but the timescales for doing this are not clear.”

      This was posted August 24, 2017, but I haven’t seen any followup, nor have I been able to find this discussion on any mailing lists. Hopefully it’s still being worked on. If not, he should change the name to Tile Windows instead.

      Quote link:

      October 13th, 2017 at 02:03

  10. Lorenzo Gatti

    I understand the sound security reasons to retire “old style” Firefox add-ons, but failing to provide adequate replacement APIs before the transition suggests that the real purpose is emulating Chrome, supporting their very limited web extensions, without caring for more advanced needs.

    Personally, I’m rushing to write an extension to replace Save-to-Read and Browse Periodically, which are the non-negotiable backbone of how I use Firefox. I had started that project a long time ago, when the retirement was announced, but I had stopped in anger given the unavailability of relatively large, not deleted randomly, and reliably transactional data storage. This time the available web extension APIs are slightly less pathetic and I’m going to experiment with using (abusing) bookmarks, apparently the only way out of the flaky storage ghetto.

    October 6th, 2017 at 03:08

  11. Branko

    Will something change on Android too? The janky scrolling experience is the one thing keeping me using Firefox on my devices.

    October 6th, 2017 at 07:44

    1. Dan Callahan

      Many of the improvements in Quantum will also benefit Firefox for Android, though much of the focus for version 57 was specifically tailored toward the desktop version of Firefox.

      October 7th, 2017 at 12:02

  12. Tim

    My Mozilla Firefox browser has stopped working.
    I have Chrome, but it is definitely not my favorite browser.

    How do I make Firefox work again?


    October 6th, 2017 at 08:09

    1. Dan Callahan

      I’d recommend starting with these troubleshooting instructions.

      October 7th, 2017 at 12:04

  13. Michael Carper

    How can I move the tabs to be below the URL bar in 57?

    October 6th, 2017 at 08:11

    1. Dan Callahan

      There isn’t an officially supported API for that in Firefox Quantum. Sorry :( You might be able to achieve that by tweaking the (not-officially-supported) userChrome.css file. The subreddit over at /r/FirefoxCSS is a good place to start.

      October 7th, 2017 at 12:05

  14. erick

    Before installing flash Firefox would use whatever to play the content on one modern website. However for another older website non of the video’s played unless I had flash installed because it only recognizes flash. So I installed flash leaving it to turn off when not in use in the settings. Ok so now I return back to the modern website and find that no animation plays because its not using its native inbuilt extensions on Firefox but instead is defaulting to flash ? Whats going on ? The modern website used to have flash but somehow updated to HTML5. I don’t have this problem on Youtube, because the browser uses HTML5 not flash.

    October 6th, 2017 at 08:28

    1. Dan Callahan

      Can you share URLs to those sites so I can see if I can reproduce the problem on my end?

      October 7th, 2017 at 12:07

  15. Tired

    Many shops wait until the last possible moment to put out or develop a new version for the new apis, even if their extensions and a near direct port from chrome. Mozilla has been blogging and putting out PR notices at increasing frequency for the majority of this year that yes, legacy add-ons are going away. They’ve been saying it’s going to happen for years at this point, but the app support wasn’t there. If the legacy doesn’t go away, there’s no incentive to put in the effort to switch.

    The APIs don’t support some use cases yet which is unfortunate and ultimately impacts users. I don’t know what the right path forward is. Maybe scare devs a couple times as we near the deadline, back off a couple of times till all the largest extensions are supported or have alternatives then flip the switch. Maybe offer an “upgrade” path to ESR if the users don’t have alternatives to switch to. No matter what, is users will lose extensions, just hopefully not one’s a lot of people care about.

    For me:
    I use LastPass (as a foolish paying user) and adblock plus because I like the idea of having ads that aren’t in my face. Neither really works in ff57 yet. I switched to ublock origin and it works just as well. No replacement for LastPass other than using old Firefox, but I’m eyeing alternative password managers since their extension in Firefox 55/56 is full of bugs anyway.

    October 6th, 2017 at 09:08

  16. Alex B

    “existing 32-bit installations will automatically upgrade to 64-bit builds if supported by the underlying hardware.”

    This is probably going to screw us up, is there a way of stopping it?

    (We seem to be relying on a bank auth plugin for which only the 32-bit version actually works). At least, I think that was the issue – will check with colleagues.

    October 6th, 2017 at 09:45

    1. Dan Callahan

      You can manually download 32-bit builds of Firefox if 64-bit will be problematic for you. However, we completely removed plug-in support last year, with the exception of Flash, so things shouldn’t break for you.

      Firefox ESR (“Extended Support Release”) is currently based on Firefox 52 and will continue to receive security updates and support plug-ins until May next year.

      October 7th, 2017 at 12:12

      1. Alex B

        Re plugins, sorry, I used the wrong terminology. It is not a browser plugin but a pkcs#11 module (which is a dll on windows, and hence 32/64 bit specific). See
        I will check what happens with this…

        October 8th, 2017 at 08:55

  17. ddd

    Firefox will be look like Edge so why i have to use firefox not chrome or vivalid ?

    October 6th, 2017 at 18:08

    1. Dan Callahan

      Looks are just one reason to use a browser. We hope you’ll choose Firefox because it’s faster, more responsive, more customizeable, open source, and made by a non-profit that’s dedicated to keeping the Internet open and standards-based.

      October 7th, 2017 at 12:15

  18. Andrew

    Do you remember what happened to Netscape? Netscape in the day was my browser of choice for many years until they over bloated it and ruined it with a bunch of crap that no one needed. Welcome to the present and you are you following down the same path. I updated to V56 and suddenly all my saved screenshots and even my saved open office documents now have change preferences for the opening applications. Why do think anyone needs screenshot embeded in the browser when the Mac and PC has always provided that feature directly anyway? Who are you to think that you can go on my machine and dictate what software I use to open any of my files? I am going to revert to an older version of Firefox and when that stops working I will look for another replacement. I suggest you take a serious look at where you are heading and a look at past Netscape history. Good Bye.

    October 6th, 2017 at 18:37

    1. Dan Callahan

      It’s absolutely not our intent to “go on [your] machine and dictate what software [you] use to open any of [your] files.” I’m not sure what setting got changed or why, but you can always review, reset, and modify file type associations in Preferences -> General -> Files and Applications.

      We now run Test Pilot experiments to validate features before adding them to the browser, helping to ensure that we don’t add “a bunch of crap that no one needed.” In the case of screenshots, we saw a strong, positive reaction from our testers.

      Even though “the Mac and PC has always provided [screenshots] directly anyway,” Firefox Screenshots offers two major features that are only possible inside-the-browser.

      1. It’s possible to take a screenshot of the full page in one command, even if the page is very long and otherwise scrolls beyond the visible on-screen area.
      2. By integrating with the browser, we can use the DOM tree to assist in selecting blocks of content on the page, removing the need for a steady hand or cropping the screenshot in Photoshop afterwards.

      Rather than reverting to an older version, I’d suggest you try a newer version instead. Give Beta, Developer Edition, or Nightly a spin and you might be pleasantly surprised at its speed and responsiveness.

      October 7th, 2017 at 12:27

      1. Konstantin

        The problem with the transition is it won’t be painless.

        After upgrading to FF 56 I spent hours trying to make the damned thing work (it started to segfault; I had to remove all extensions and, finally, create a new profile and re-configure everything, adding extensions back, one by one). FF 55 was working perfectly with extensions I use; FF 56 failed to do so.

        FF 55 was working fine with bookmarks backups; FF 56 failed to load bookmarks backups (FF devs confirmed the bug – when loading bookmarks, not all parameters possible values were properly checked – hence the process was aborted, see bug #1404631).

        So yes, you are trying to dictate what to use and what not to use, phasing out features you consider improper, without actual thorough testing.

        Nothing will be painless, except probably for your “spherical ideal testers in vacuum”.

        October 9th, 2017 at 17:32

  19. F

    Will there be Classic Theme Restorer? Without that there is no point not to use crappy chrome or perhaps Vivaldi.

    October 8th, 2017 at 09:10

  20. Konstantin

    > In most cases, the upgrade to Firefox Quantum will be painless.

    Correction: in quite a few cases. FF 56 began with segfaulting over one of absolutely harmless extensions; I had to completely wipe out profile to make the new version work. Painless, you are saying? Previous upgrades were more or less painless. FF 56 is already a disaster, costing me several hours to make it work as I expect.

    Judging by how many extensions will be phased out, judging by “The APIs themselves are also still being developed and expanded, so expect to see greater capabilities with each release of Firefox.”, every next FF upgrade will bring more havoc and incompatibility issues, until your API is more or less stabilized.

    FF 56 has also brought a “nice” case of bookmarks backups from previous version that can’t be restored any more.

    Methinks, QA phase is either severely neglected, or the overall FF quality is degrading as developers try to bring new platforms as fast as possible, sacrificing FF stability and core functions that didn’t fail before.

    October 8th, 2017 at 20:21

  21. Megaman

    Firefox 56 was the last version to have Restart with CTRL+ALT+R, what is the new command?

    October 9th, 2017 at 20:27

  22. byteme

    Good to know that Firefox 56 is the last version to support web extensions. Now I just need to find a way to block updates so I never have to use 57 and up. If I wanted to use chrome Id use it… but you just had to copy the worst parts of it didn’t you…

    October 10th, 2017 at 12:07

  23. Edi

    Firebug does no longer work… An yes, there is the Inspector. But he cannot do, what Firebug has done. If it will not be drastically improved in the near future, this could be the end of Firefox for website developers. In the meantime I use older versions of Firefox, Pale Moon or Chrome.

    October 11th, 2017 at 01:15

  24. Ellis

    So, is there still a way to search all the javascript files that loaded with a page? I used to be able to go into the debugger and use ! to search all files, but Firefox updated itself to 56 for me today and that no longer seems possible. You even avoid doing that sort of search in the video.

    October 11th, 2017 at 14:24

  25. subramaniam

    installed firefox quantum beta on my 32bit machine with 4gb ram.

    it been consuming around 1.3gb of ram after few minutes and when i end task the specific firefox process that consumed 1.3gb, it was Facebook.

    is there any workaround to reduce memory usage ?

    October 12th, 2017 at 13:07

  26. Vladamir Dvorak

    Please add support for tab groups

    October 13th, 2017 at 04:32

  27. Hal Newman

    Quantum Beta is awful. I can’t believe it. So many extensions no longer function – including several absolute dealbreakers. Performance has suffered greatly. Everything is so much slower. How do I get back to the previous version of Firefox? Failing that I will be migrating to Chrome… I have been a big supporter and loyal user of Firefox however at this point I am shaking my head in disbelief.

    October 13th, 2017 at 10:09

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