Mozilla Firefox 95.0 release: here is what is new

Martin Brinkmann
Dec 7, 2021

Firefox 95.0's release date is December 7, 2021. It is the last major stable release of Firefox in 2021. Firefox 95 includes several new features and improvements, but also bug fixes and security patches.

The other Firefox channels, Firefox Beta, Dev and Nightly, Firefox ESR and Firefox for Android, are also updated around the same time of a new stable release.

Firefox Beta and Developer editions are moved to version 96, Firefox Nightly to version 97, and Firefox ESR to version 91.4.

You can check out the release overview for Firefox 94.0 here.

Executive Summary

  • Firefox is available on the Microsoft Store officially now.
  • The new release reduces CPU usage and power usage on Mac OS X in some use cases.
  • Site Isolation is enabled for all users.

Firefox 95.0 download and update

Firefox 95.0 is downloaded and installed automatically on most devices that run the browser. Desktop users may run manual checks for updates to get the version as early as possible, Android users will have to wait until Google Play pushes the release to their mobile devices.

On desktop systems, select Firefox Menu > Help > About Firefox to display the version of the browser that is installed currently, and to run a manual check for updates.

Firefox 95.0 new features and improvements

RLBox sandboxing technology for all platforms

RLBox is a new sandboxing feature that Mozilla integrated in Firefox 95. It is designed to "isolate subcomponents to make the browser more secure". Mozilla developed the technology in collaboration with researchers at the University of California San Diego and the University of Texas.

RLBox isolates the following five modules in Firefox Stable in this initial version: Graphite, Hunspell, Ogg, Expat and Woff2. Mozilla notes that the technology allows Firefox to treat the modules as untrusted code, which, provided that the implementation is correct, could protect against 0-day vulnerabilities in the browser.

Check out the article about RLBox on the Mozilla Hacks website for additional details.

Site Isolation in Firefox Stable

Originally scheduled for Firefox 94, Site Isolation should now be available to all users of Firefox Stable. Here is the info that I wrote for the Firefox 94 release article:

Mozilla started to test Firefox's Site Isolation feature in Firefox 70, and rolled it out in Firefox Nightly in September 2020. Called Project Fission internally, site isolation aims to improve privacy and security significantly by isolation webpages and third-party iframes.

Site Isolation builds upon a new security architecture that extends current protection mechanisms by separating (web) content and loading each site in its own operating system process.

This new security architecture allows Firefox to completely separate code originating from different sites and, in turn, defend against malicious sites trying to access sensitive information from other sites you are visiting.

Other changes

  • The Picture-in-Picture button can now be moved to the opposite side of the video.
  • CPU usage of Firefox on Mac OS X and Windows Server is reduced during event processing.
  • Power Usage of Firefox on Mac OS X is reduced, especially when fullscreen mode is enabled (including when watching video streams, e.g. on Netflix or Amazon Prime).

Developer Changes

  • The global attribute inputmode is now supported on all platforms and not just on Android. It provides hints about the virtual keyboard that is best suited for a specific task.
  • The Crypto.randomUUID() function is now supported. This returns a cryptographically strong 36 character fixed-length UUID
  • The CSS cursor property is now supported on Firefox for Android

Enterprise changes

Not published yet.

Bug Fixes

  • Users of the JAWS screen reader and ZoomText magnifier don't have to switch applications after starting Firefox in order to access the browser.
  • ARIA switch role states are now reported correctly by Mac OS VoiceOver.
  • Faster content process startups on Mac OS.
  • Memory allocator improvements.
  • Page load performance improvements by "speculatively compiling JavaScript ahead of time.
  • User-Agent override for, which allows Firefox users to use more features, e.g. Call features, and access Huddles.

Known Issues

None listed.

Security updates / fixes

Security updates are revealed after the official release of the web browser. You find the information published here after release.


Firefox 95.0 is the last 2021 release according to the schedule. It is possible that a minor update will be released, but the next major version of Firefox, Firefox 96.0 Stable, lands on January 11, 2022.

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Mozilla Firefox 95.0 release: here is what is new
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Mozilla Firefox 95.0 release: here is what is new
Firefox 95.0's release date is December 7, 2021. It is the last major stable release of Firefox in 2021. Firefox 95 includes several new features and improvements, but also bug fixes and security patches.
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  1. Richard Benish said on December 27, 2021 at 12:18 pm

    You can choose from a bazillion color schemes. But if you’re not geeky enough to tinker with the code, you cannot remove the annoyingly wasteful Tabstrip at the top.

    I once made the mistake of buying some pants whose pockets would empty their contents when sitting on a soft chair. The wasted 1/2 inch of vertical space in the newly wrecked Firefox browser causes me to group software designers in with fashion designers as among my least favorite people.

  2. Rex said on December 12, 2021 at 1:33 pm

    Imagine using a ‘privacy respecting’ browser that requires you to go over about:config after every new version to ensure your settings haven’t been reset.

  3. TelV said on December 11, 2021 at 11:34 am

    I have a couple of minor issues. I would like to add the bookmarks button to the toolbar to open them in the sidebar. But because the description is so long it pushes anything else to the right of the description out of the way and becomes invisible itself. Here’s a couple of images to illustrate the problem.

    Having to use Ctrl+B everytime just adds to the irritation.

    The other gripe I have which is a bit more serious is that glyphs show instead of box where the user has to checkmark an item on a site where the language isn’t English. In those circumstances I have to switch to another browser.

    Oh, and last but not least, why has Moz removed the option to use the backspace key to go to previous pages. It’s just not convenient to have to use the Alt+left arrow every time.

  4. Ram Store said on December 9, 2021 at 5:18 am

    How the **** do I search for VALUES in about:config? Not the preference name, but the string present in the value.

    No, F3 doesn’t cut it because the listing (screen) includes all the values and is confusing.

  5. Shiva said on December 8, 2021 at 8:21 pm

    I was updating user.js, I see that there are changes regarding WebRCT and also the page of recommended extensions has undergone some changes.

    1. TelV said on December 11, 2021 at 11:41 am

      Do you mean WebRTC? In about:config “media.peerconnection.enabled” is still showing as “false” on my system.

      1. Shiva said on December 11, 2021 at 3:03 pm

        As a far I know “media.peerconnection.enabled” is set to “True” by default when you create a new profile. In arkenfox user.js v95 it has been made inactive.

        uBlock Origin 1.38 also removed “Prevent WebRTC from leaking local IP addresses” from settings:

        Have you resetted inactive prefs with prefsCleaner? Maybe you have another extension like Chameleon with this option still enableb. However I’m not the right guy to ask.

        It was the first change I noticed and I remeber this wiki:
        I’m also became a fan of ‘Don’t Bother…’, anyway these are all good and updated suggestions but users are generally not obliged to follow them slavishly I suppose. Most likely its like what you wrote about dFPI.

    2. Yash said on December 9, 2021 at 9:23 am

      Yep, biggest surprise is no Temporary Containers. Not just that apparently dFPI has matured enough to replace FPI.

  6. moon3x said on December 8, 2021 at 3:56 pm

    How to disable telemetry in firefox(or palemoon) about:networking shows two options:

    1. Rex said on December 12, 2021 at 1:32 pm

      Pale Moon doesn’t have any telemetry, dumbass. That’s a Firefox and Chrome specialty.

  7. Anonymous said on December 8, 2021 at 9:46 am

    Good old Firefox.

  8. nealis said on December 8, 2021 at 7:55 am

    I wish Google would do something about the cluster!@#$ of zero days plaguing Chromium code base, it is bad enough to make you consider switch to Firefox. However while Firefox desktop is pretty good, all their Mozilla ecosystem android and IOS are technically backwards or compromised by google money.

    Mozilla offers adblock on their nonflag forks like Firefox Focus but not on their main browser b/c their google overlords wouldn’t like that. In comparision even Microsoft has built in adblock for their mobile offerings.

    1. Iron Heart said on December 9, 2021 at 1:11 am


      > I wish Google would do something about the cluster!@#$ of zero days plaguing Chromium code base, it is bad enough to make you consider switch to Firefox.

      Good luck, won’t improve your security:

      If Firefox wasn’t totally irrelevant and hackers actually cared enough to take a look at it, they would have as many securities as Chromium, likely even more.

    2. Yash said on December 8, 2021 at 9:06 am

      Take it easy. ETP is available on both Focus and main Firefox, so end result is same. Focus is more of an open site and leave it – all your history will be cleared browser. Main Firefox is much more rounded. But adblocking is same on both.

      1. Nealis said on December 9, 2021 at 12:33 am

        @Yash Firefox focus has full AdBlock, not just etp

      2. Yash said on December 9, 2021 at 9:20 am

        Last time I checked it which was hours ago, Focus had ETP as adblocking solution same as main Firefox.

    3. Anonymous said on December 8, 2021 at 8:48 am

      They are getting a bigger spreadsheet to hold all the chome|ium zero days

  9. Euphoria Hunter said on December 7, 2021 at 11:44 pm

    Firefox is great, but each time I use it I find myself going back to chromium based browsers because of usability annoyances and lack of basic features such as remapping keyboard shortcuts, search inside plugins page, moving extension icons among others, even some plugins which I depend on in chrome, are not available and cannot be installed in FF. IMO Opera gets this best, although for privacy reasons I stopped using it a while ago.

  10. JohnIL said on December 7, 2021 at 8:32 pm

    Used to use Firefox on Linux and Windows 10. Found it to be terribly slow and a RAM hog. I thought Chrome was the only RAM hog? After seeing a lot of web benchmarks leaving Firefox in the dust. I wish Mozilla would focus a lot more on performance and not just saving me from myself using the web.

    1. Joe said on December 8, 2021 at 5:33 am

      @JohnIL: I used to quit Firefox because of performance issues, but I would always come back (there are more and more vertical tab options, but nothing in any other browser has been able replace Tree Style Tabs for me).

      Since the last time I came back, sometime in 2020, I have not noticed any performance issues at all.

    2. Anonymous said on December 7, 2021 at 8:57 pm

      @JohnIL well, memory is bought and used to get filled… memory hog is not a measure to say a browser is better than the other, unless the browser is using 75% of your memory then who cares? memory not used is memory wasted and until you are not in the 90s percent, it will not use the disk.

      Now, if we talk about CPU, Chromium browsers (most) are better than Firefox because if you open tabs with heavy garbage websites full of JS or with videos and all, the cpu on chromium browsers will be decent, but trying to do that with Firefox the CPU will never stay low.
      Use Profiles in a chromium browser and now use Profiles in Firefox and you will tell the difference even more, since Firefox is pretty bad at that, even the famous containers are just inefficient, they are convenient in the way you can log in with different accounts, but it is also CPU inefficient.
      CPU usage matters because it will consume more energy, slow the computer etc etc.

      I haven’t used Firefox in a while, I only tested LibreWolf and modify it to make it usable and not “we locked everything up for you” type of browser, and people say LibreWolf is lighter on resources. But I found it to be meh when it came to have multiple tabs open and doing what I normally do.
      Also if we include I also disable sandbox and all the useless “protections” that are just marketing because I will never be affected by some “vulnerability”… I probably have more chance of dying by a chupacabra than being affected by any of those vulnerabilities which I don’t even care anyway. So Chromium uses less resources and feels a little faster.

  11. Tom Hawack said on December 7, 2021 at 6:57 pm

    Question regarding RLBox.

    RLBox uses WebAssembly to isolate potentially-buggy code.
    Does the WebAssembly pref (javascript.options.wasm) need to be enabled (true)?
    I believe the answer is ‘no’ but I’d rather be sure.

    Personally I disable WebAssembly yet have installed a toggle toolbar button to enable it on sites which require it, i..e.[].

    1. Sol Shine said on December 7, 2021 at 7:46 pm

      @Tom Hawack
      You do not need to have WebAssembly enabled.

      Info from Mozilla:

      The core implementation idea behind wasm sandboxing is that you can compile C/C++ into wasm code, and then you can compile that wasm code into native code for the machine your program actually runs on.  These steps are similar to what you’d do to run C/C++ applications in the browser, but we’re performing the wasm to native code translation ahead of time, when Firefox itself is built.

      You could distribute the wasm code and compile it on-the-fly on the user’s machine when Firefox starts.” We could have done that, but that method requires the wasm code to be freshly compiled for every sandbox instance.  Per-sandbox compiled code is unnecessary duplication in a world where every origin resides in a separate process. Our chosen approach enables sharing compiled native code between multiple processes, resulting in significant memory savings.


      1. Tom Hawack said on December 8, 2021 at 10:02 am

        @Sol Shine, Roger, we copy you on the ground. Thanks
        I had read the information you quote but remained uncertain if that implied that the WebAssembly pref needed or not not to be set to true.

  12. Nico said on December 7, 2021 at 5:28 pm

    Fission was not enabled here by default…
    ‘fission.autostart —> ‘false’

    (Linux; Dutch version)

    1. rollout bot said on December 8, 2021 at 3:24 am

      The rollout is via experiments where they can control the platform and percentage, so if you have that disabled you’ll have to wait for it to be set by default in 97. windows/mac are at 100% and linux at 50%

    2. Tom Hawack said on December 7, 2021 at 6:42 pm

      I’ve enabled Fission starting FF94 when it was disabled by default. No problem here with Win7.
      Still disabled on this latest FF95?

      // Enable Fission
      // Fission is Mozilla’s implementation of Site Isolation in Firefox []
      // NOTE 1 : REQUIRES gfx.webrender.all=true
      // NOTE 2 : DO NOT EDIT ANY OTHER “fission.*” or “gfx.webrender.*” PREFERENCE.
      pref(“fission.autostart”, true); // DEFAULT=false

    3. Anonymous said on December 7, 2021 at 5:33 pm

      > Fission was not enabled here by default…

      Same for me on both portable and regularly installed version (95.0, EMEfree, en-US)!

      1. Nico said on December 7, 2021 at 6:34 pm

        Even stranger, it wasn’t even enabled on Nightly, which got updated to 97 today.

      2. Disk said on December 7, 2021 at 6:38 pm

        If you check about:process, it will likely be enabled even without enabling it deliberately from config, just like webrender, other than that it’s a gradual rollout so it might get enabled a bit later on your specific device

  13. Artem S. Tashkinov said on December 7, 2021 at 5:03 pm

    ui.systemUsesDarkTheme=1 in Firefox 95 breaks multiple websites, as well as Firefox itself, darn.

    I had to disable it.

    1. Philippe L. said on December 8, 2021 at 5:21 pm

      @Artem S. Tashkinov
      You can delete “ui.systemUsesDarkTheme”, Firefox doesn’t seem to use it anymore.

      I am using Firefox 95 on Windows and have found that many sites are now in dark mode if the Firefox theme is dark.

      But i found an explanation and a solution on bugzilla :
      ? about:config
      ? see “layout.css.prefers-color-scheme.content-override”

      0 = dark (users may want a light system style, but dark websites)
      1 = light (users may want a dark system style, but light websites)
      2 = system
      3 = browser theme (Firefox 95 -> “new ?” default original setting = 3)

      1. bk said on December 14, 2021 at 5:51 am

        Bless you. This was so annoying

    2. Artem S. Tashkinov said on December 7, 2021 at 5:04 pm

      That’s under Linux, maybe Windows/MacOS users are not affacted.

  14. Peacock365 said on December 7, 2021 at 2:11 pm

    What will madaidan’s misguided followers spew about now with Site Isolation and RLBox

    1. Anonymous said on December 8, 2021 at 3:21 am

      > What will madaidan’s misguided followers spew

      Iron Heart responds. Hilarious and pure comedy gold

      1. Iron Heart said on December 8, 2021 at 11:16 pm


        > Iron Heart responds. Hilarious and pure comedy gold

        Responding again to amuse you further, good sir. There is no “madaidan movement”, so he can’t have any “misguided followers”. The guy is running a website giving you factually correct information about Firefox’s state of security or rather lack thereof (thanks for the shoutout btw, here it is: ) – nothing more and nothing less. I imagine you hate this type of info, but all I can say in response to this is: Get a grip on reality and move on.

      2. Nihal365 said on December 9, 2021 at 1:59 pm

        @Iron Heart

        > There is no “madaidan movement”

        It’s right. There is no movement. There is only one ignorant peacock who spam technical notes of some researcher, on topics that this peacock has no idea about, and can only copy and paste smart phrases – nothing more and nothing less, pretending to be very concerned about hackers and security.

    2. Iron Heart said on December 7, 2021 at 9:18 pm


      > What will madaidan’s misguided followers spew about now with Site Isolation and RLBox

      Maybe that Firefox slowly catches up to Chromium but still lacks behinds in many areas of overall application security, i.e. reality?

      1. m3city said on December 7, 2021 at 11:47 pm

        @Iron Heart
        Does chrome have sth similar to RLBox? Check out that blog post. This (unnoticable for user) technology may not be called shattering, but still it’s sth good.

      2. Brandon said on December 14, 2021 at 3:20 pm

        Please write sentences that make sense, using real language instead of stupid, lazy texting words. sth is an abbreviation of south so what does “..have south similar to..” or “..still it’s south good.” mean ?

        I can figure out what you MEANT due to context but please, stop being lazy and adding to the dumbing down of humanity and adding to the language cesspool that the internet has become. There are complete words in English for a reason, so that all readers who comprehend English can understand what has been written. If you must use abbreviations, please stick to established ones, again in the name of comprehension.

    3. Nihal247 said on December 7, 2021 at 5:22 pm

      I am switching to Firefox as the superior browser for privacy and security – chromium’s security is too weak

      1. Timmy said on December 7, 2021 at 9:03 pm

        LOL sure… let’s pretend you are switching and you are not just an ignorant fanboys talking what you have no idea about and make it sound like a fact.
        Also, keep pretending using a browser will somehow get you privacy when you are connected to the internet, if you didn’t have much privacy before internet, less now when even refrigerators want you to be online.
        And about security… show proof about it, most security risks are just stuff that will not affect 99.9%, most need physical access to the computer and people probably will fall from phishing email rather than having some vulnerability coming across their devices.

        Stop being a fanboy and maybe you will learn 1 or 2 things, I am sure you have some instagram or twitter or reddit or discord or something that is less than private and you probably don’t care about it, so why do you even worry about what browser you are using anymore?

        Firefox performance is worst than any chromium browser, even Vivaldi, I would think that is more important than some fake marketing scheme like “privacy” and “security” which are fake statements incompatible with internet in 2021.

  15. Anonymous said on December 7, 2021 at 1:51 pm

    If Mozilla Corporation was really interested in solving that type of security problems it would have ublock origin pre-installed on Firefox. But it’s only a Google puppet that has as a greater priority to keep the ad industry well fed.

    1. MW said on December 8, 2021 at 3:46 am


      Mozilla likely doesn’t do that because Firefox is still used in a ton of corporate and educational organizations where having something like uBlock Origin pre-installed, pre-configured may lead to issues with internal or external websites through no fault of the uBlock developers, filter maintainers, or the Firefox team. Brave doesn’t have to worry about that because I doubt Brave is widely installed on corporate/government/education systems like Firefox still is.

      I’m not saying you are wrong or anything, just that I suspect that is the reasoning for Mozilla NOT taking that action even more than the Google search deal.

    2. m3city said on December 7, 2021 at 11:40 pm

      The “puppet” master plans not only to chop off limbs of adblockers by manifest no.3, but flocks users of their browser to cohorts (by similiarities). I’m really curious how it’s done. It has to be really good at spying and profiling users. And isn’t google the biggest ad-fuelled corporation on earth? :)

      1. Iron Heart said on December 9, 2021 at 1:05 am


        Instead of crying out loud, why are you not looking at solutions?

        > chop off limbs of adblockers by manifest no.3

        Who cares? There are Chromium-browsers with internal adblocking, and there are other methods of adblocking as well, i.e. system- or network-wide.

        > but flocks users of their browser to cohorts (by similiarities)

        Again, this is disabled in various Chromium-based browsers.

        If you install Chrome, this is your fault. Don’t blame Chromium which is open source and can be, and has been, modified.

      2. m3city said on December 9, 2021 at 8:59 am

        @Iron Heart
        I said no thing about chrome or chromium, browsers based on that. My response was in the corporate world of things. And it’s true, as is yours naturally.

    3. Anonymous said on December 7, 2021 at 5:20 pm

      So network partitioning across the board and rolling out Total Cookie Protection to all users is “keeping the ad industry well fed”? You have a fucked up and ignorant view of things. Adblocking as tracking is redundant.

      Not only is it the adblocking tracking redundant, but why should Firefox pre-install it and then deal with tens/hundreds of thousands of reports of things not working or take on added risk (third party lists). Firefox is not out to destroy advertising and does not seek to hold content creators or advertisers to extortion, unlike Brave – Brave doesn’t care about adverts, they only care about monetizing them for themselves to support their scammy crypto BATshits

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