Updating to Firefox 96

Yesterday we announced a new partnership with Mozilla and a transition to Mozilla default settings in Firefox 96. If you didn’t read this announcement yet, please visit https://blog.linuxmint.com/?p=4244.

Today, in preparation for Firefox 96 I want to make one more blog post, this time to talk specifically about technical details and to help people before, through and after the transition.

Firefox 96 is out today but we’ll publish the update on Friday January 14th. This will give everyone a few days to read this post, prepare for the update and get an opportunity to ask questions and seek help before the transition.


Impacted releases

This post is relevant for users of Linux Mint 19x, 20, 20.1, 20.2 and LMDE 4.

In Linux Mint 20.3 the transition already took place with Firefox 95 during the BETA (https://github.com/linuxmint/mint20.3-beta/issues/47).

Impacted browsers

Only the repository version of Firefox is impacted.

The flatpak version of Firefox already uses the Mozilla default settings. The Mozilla version (downloaded from their site) obviously also already uses it as well, and so do versions from PPA (ESR or not).

Other browsers are not impacted.

Nature of the changes

If you used Firefox in Windows or other Linux distributions you’re already familiar with Mozilla’s default settings.

We’re transitioning towards the same configuration as the one which is used everywhere else. The most noticeable changes are the search engines, the start page, and the preferences settings.

Impact on configuration (technical explanation)

The main impact is on the configuration. Because of the way settings work in Firefox, only settings which value is different from the default value are actually stored in your profile. As the default value changes, you can lose some configuration.

Say a particular setting defaults to A in Linux Mint but B in Mozilla. If you set it to C, then your profile contains a custom value. As we transition the default from A to B, you keep your C custom value.

Now, say you have it set to A. Since it’s identical to the default value, it is not custom, and so it’s not stored in your profile. To you it may look like something you set, but really you’re just using the default value, so this is actually not “set”. As we transition the default value from A to B, you simply transition from no custom value to no custom value, and thus also transition from A to B. From your own point of view this can create a gap between your expectation and the resulting configuration.

Before the update

Before the transition, make a backup copy of your profile and perform a system snapshot. This guarantees you’ll be able to go back and essentially removes any risk of losing anything.

System snapshot

To create a snapshot, open Timeshift and hit the Create button.

Profile backup

To make a backup copy of your profile, open a terminal and type:

cp -R .mozilla .mozilla-backup

Custom Policy file

Our packages will provide a policy file in /usr/lib/firefox/distribution/policies.json.

If you created a file under that path, it will be overwritten. Make a copy of it.

After the transition you can place your policy in /etc/firefox/policies instead.

After the update

Review your settings

In Firefox click on Settings and go through the tabs on the left to review your settings.

Set things to your liking and select your favorite search engine.

Spell check and dictionaries

On any website, right-click in a text area (i.e. a zone where you can enter text) and select “Languages”.

If you don’t see your language, select “Add Dictionaries…”.

Alternative solution

Alternatively, reinstall the package for your Firefox language pack. Type this command in a terminal to list your language packs:

dpkg -l firefox-l*

And then for each pack:

apt reinstall pack-name

Replace pack-name with the appropriate pack name. For instance, to reinstall the French language pack in Linux Mint, the command would be:

apt reinstall firefox-locale-fr

If you had added words to your dictionary and they are missing, look for a file called persdict.dat in your profile backup and copy it to your profile.

Custom Chrome CSS

If you had a custom chrome/userContent.css file and it goes missing, copy it over from your backup profile and enable the following setting in about:config:


Warning messages

Firefox cannot handle its own updates. It doesn’t know how to check the repositories and doesn’t have admin privileges anyway. In Linux Mint this is the job of the Update Manager so Firefox is told not to handle updates.

In the past, this was done via code changes. We patched Firefox not to do it and not to show any warning about it. This is how it is in Debian and Ubuntu as well.

With this transition this is done via a policy file, i.e. via system-wide configuration. Firefox shows the following messages in the preferences and in the about dialog as a result:

These messages can be quite confusing, especially the first one. Please ignore them for now. We’ll be reporting the issue to get it fixed upstream.

Comments section

The comments section on this post is exclusively dedicated to support. If you have questions, or you need help about the technical aspects of this transition then this is the right place.

We can’t “move” off-topic comments to the appropriate post here with WordPress. If something is off-topic we can either let it harm the topic or moderate it. Please respect this so we have this space to interact on support and technical questions don’t get lost.

To talk about Firefox in general or the partnership with Mozilla comment at https://blog.linuxmint.com/?p=4244 instead.

For any other topics use the forums or the other posts on this blog.

Thank you for your understanding and if you’re waiting on this update for your patience. I wish you all a smooth update and I hope you’ll enjoy your experience with Mint and Firefox after this transition as much or even more than before.


  1. Under Firefox Settings > General > Firefox Updates are two options:
    One, set as default, is “Automatically install updates (recommended)”.
    The second is “Check for updates but let you choose to install them”.
    Will choosing one or the other have any different effect on updating from the Mint repository?

    1. I had the same on one of my machines, despite identical user profile. Firefox sometimes seems to ignore the system policy that Clemens described, but maybe only for display. You can back up your user profile ./mozilla, then delete ./mozilla, then start Firefox which will generate a new user profile. The automatic updates will show up as disabled. Now you can quit Firefox, delete the freshly generated ./mozilla, replace that from the backup you made, and start Mozilla again. That worked for me, but I needed to do that a couple of times. No idea why, but suddenly, Firefox showed the updates as disabled like it should.

    2. Hi Terry,

      No, it makes no difference. First, it doesn’t supersede the Update Manager (and apt/dpkg backend). Second, Firefox cannot update itself anyway, it doesn’t have the administration rights to do so. These options are relevant to Windows users and user installations where the OS doesn’t handle such updates. It’s not relevant to system-wide installs such as the ones done in Linux distributions where the package management system takes care of updates.

      After the update this will show “Updates disabled by your system administrator”.

  2. Don’t understand what’s the big fuss about, when I will see the update ready in the repositories, I will delete my FF profile I reconfigure again everything + loggings everywhere in 15 minutes. If I have to work a little just to have everything clean and tight, so be it

    1. Communication is needed when software doesn’t meet expectations, even more so when something isn’t reversible. Without a profile backup and a snapshot this isn’t reversible. It’s not critical but it can be frustrating.

      It’s nice to explain defaults also. The way settings work isn’t obvious. People can be quick to suspect foul play and malice when they think their settings were changed on purpose.

      Note: If you ditch your profile you don’t just lose your configuration, you lose your history, saved passwords, bookmarks, etc. I’m sure you’re aware of that already, but I wanted to make it clear in case people want to do the same.

    2. With regard to Clem’s mention of loosing bookmarks, among other things, isn’t possible to simply open Bookmarks, click on Manage Bookmarks, and use the Import/Backup function in the top menu? Am i wrong about that?
      Yes, I’m one of those people that isn’t 100% comfortable using the terminal.

  3. Hello Clem,
    About the custom CSS issues – there is this property in about:config – toolkit.legacyUserProfileCustomizations.stylesheets. It enables using userChrome and userContent files, but is default to false in Mint 20.2 / Firefox 95.0.1. I think Mozilla team changed it so since a long time. People should change it to true and copy their files again (if missing).

  4. Remember you can also create a “user.js” file – in your profile directory – to store many settings and changes (including all the settings referenced by Pjotr on the Easy Linux Tip Project). I’ve found this works for about 90% of the changes I would otherwise make.

    As someone who uses multiple profiles it makes it real easy to customize for each profile if needed.

    Fwiw, another dumb FF trick I’ve used for years is to create a “profiles” directory in my home folder (or on my Data drive) separate from the standard dir. Then it’s just a matter of starting the profile manager (firefox -profilemanager), create new profile (point new profile to correct place), start browsing.

    If you do that, you can also back up the profiles.ini file (~/.mozilla/firefox/) which has the info on your profile locations

    Nice and easy to back things up too without having to deal with the rest of the home directory

    Hope this helps

    1. Thanks. When you write something within a text area in Firefox, you can right-click -> Languages -> Add dictionaries. This brings you to the link you mentioned.

      Even though the loss of dictionaries is a regression, I think I know what’s going on here, and I suspect it’s actually a good thing. In Ubuntu language-packs change the way locales work and firefox-locale-* packages probably install these as the result of Ubuntu patches. The problem with language packs (and we see that in mintlocale also) is that they pack multiple locales together. For instance en_CA is packed with en_GB in firefox-locale-en. We lose modularity here.

      After the transition this is handled the way Mozilla versions do so I guess the language pack dictionary is no longer present.

      I’d like to get more feedback on this to make sure this is what’s happening. I’ll update the paragraph then accordingly.

  5. Will it be necessary to backup Firefox profiles before every upgrade (and reset the profile after the upgrade) every time a Firefox upgrade or minor security fix is presented, subsequent to 96.0?

    1. Hi Jeremy,

      No not at all. The reason this is happening here is because:

      – We had default settings set in Mint for Firefox which we’re removing, so defaults are changing. These defaults were specific to Mint.
      – We used to have multiple patches and code changes on Firefox. These patches changed the way Firefox behaved. Some of them were specific to Mint, some specific to Ubuntu and some to Debian. With the new version we’re running the same source code as upstream Mozilla.

      For both of these points there’s only 1 transition.

      You should never have to backup your profile. That said it’s not a bad idea to do it maybe a few times a year, just like the rest of your personal data. You can face HDD failure, bugs, wrong manipulations, etc. On the matter of bugs, we’re dealing with a very big project here and which is updated very often. Just like the kernel, this can lead to regressions. Having a backup is no harm.

  6. Hi Clem, FF 95.0.1 here, upgraded from LM 20.2 to 20.3.
    In German locale there’s only ‘Der Browser wird durch Ihre Organisation verwaltet.’ in the settings, no hint that this means ‘Updates disabled’. There’s also no hint of both in the about dialog, instead something like ‘You’re using the update-channel.’ That might be confusing in other languages as well.

  7. While I am not opposed to this change per se, I must say it feels very rushed and runs the risk of confusing many users of Mint who do not read this blog regularly. I would have much preferred to keep the custom Mint version of Firefox until the next release of Mint instead of pushing the new version aggressively like this. Or at the very least, there should be some kind of warning or notification that pops up in the OS itself that explains the change in simple terms (and no, repeating “I hope this makes sense, it’s quite technical.” does not make your explanation simple). I am a big fan of Mint precisely because of the stability and predictability it gives, so this is a disappointment.

    1. Hi Jesper,

      The paragraph on how settings work is technical but it explains why things change despite having been set previously by the user. It provides an answer to a frequently asked question. I tried to keep it simple by providing examples. Let me know if you have ideas on how to make it simpler. I removed “I hope it makes sense..”, since that doesn’t indeed simplify it.

    2. I don’t object to these changes, and I think this blog post is well thought out — but I agree with Jesper that there should have been some kind of “push” message to LM users to check this blog post.

      I only happened to land on the blog because I was reading an article about the FF 96 release linked from Slashdot, and at the bottom it mentioned the LM-Moz partnership. From that post I went to the next post; this one. While I like LM (and obviously use it), I don’t read the blog regularly, and it was just coincidence that I happened to be here in the few-days-gap between this being published and the LM FF 96 release.

      Please consider alerting LM users directly when there are posts like this that address possible unexpected settings changes. (I realize that technically these aren’t settings being overwritten but defaults changing, but as you correctly note this might nonetheless surprise some folks.)

      Thanks for this thorough post otherwise!

    3. Also please consider allowing paragraph breaks in comments…your system lumped everything I wrote into one mega-paragraph πŸ™‚

  8. Clem, regarding this statement about /usr/lib/firefox/distribution/policies.json:
    “If you created a file under that path, it will be overwritten. Make a copy of it.”

    Consider instead renaming the original to something else to preserve it for reference prior to installing the new version from Mint.

    The policies.json file reflects exactly that: Organizational/group/corporate policies. Overwriting that and not preserving what’s there seems unnecessarily risky and inviting trouble.

  9. I don’t know whether this is a stupid question but I’ll go ahead with it: if you use Firefox Sync across different systems does that create any unique problems we might have with this update? Or perhaps fix them by signing out and signing back in? I’m currently using windows to send this message and will be swapping the hard drive for one with Mint in a few days.

    1. Hi Matt,

      It could help. Though, afaik there is no “master” instance in sync, so you could be adding complexity to the situation. Whether you turn it on or not, do make a backup copy of your profile and a snapshot so no matter what you can go back and try differently if you don’t get the result you expect.

  10. I wonder if there is anything like a way of diff’ing the configuration, and compare what changed between my previous settings and settings after upgrading Firefox. This would be of great help for users migrating.

    1. Hello,
      You may find one here :
      Unfortunately, it uses MS Powershell so this script language must be installed first. I guess this feature was necessary for the script to be able to run cross-platform, because “pure” bash is enough to do the job under Linux. I wrote one that works fine but I don’t intend to do much maintenance until I’ve decided what to do with it once the comparison done (merge perhaps). But if you’re a forum member and interested by this comparison module, I’ll gladly send it to you through the private channel. Was just for my ***, but would be nice if it helps someone else.

  11. This whole thing is VERY confusing to me. How will Firefox be updated if it no long gets updates from the update manager??? Where does the profile copy go? Why does this have to be so confusing?

    1. Hi Tom,

      Firefox will continue to be updated via the Update Manager.

      The profile copy ends up in ~/ (in your home folder, right-click -> Show hidden files to see it). But it’s just a copy you make, to be safe and to be able to restore. You can store it anywhere.

  12. I appreciate the announcement and your candor. But what does this mean for Thunderbird? Linux version 78.14.0 files are incompatible with 91.5.1 that the rest of the world uses. T-Bird 91 does not allow for any “extract” to a neutral format and 78 won’t accept 91 address books and mail. I’ve used T-Bird for literally decades with Windows. I’m trying to migrate 100% to Mint but I can’t because of T-Bird. Will 91 be converted to Linux or will 78 be provided a way to import 91 structures? There needs to be some strategy as not everyone wants to dual boot. I am further impaired because I have 3 Acer laptops, none of which will dual boot, but that is my problem. I just want to migrate decades of history and information to Mint. The latest versions of T-Bird on Windows and Mint are incompatible and I cannot find any indication a fix is planned or in progress. I really don’t want to go back to Windows!

    1. Hi Bob,

      Nothing’s changed for Thunderbird right now. That said, you have access to version 91 already:

      – From the ppa:mozillateam/ppa PPA. Open Software Sources -> PPA and add that PPA. Then update thunderbird.
      – As a flatpak. Open the Software Manager, search for thunderbird and you’ll find versions 91 (from Flathub).
      – As an archive you can decompress and run from anywhere (from thunderbird.net).
      – As an appimage: https://github.com/srevinsaju/thunderbird-appimage/releases

    2. At least in LMDE4 (which hasn’t received any major updates for a while), Thunderbird updates via the reliable APT process as version 91.4.1 already.

      So there is no need to use any insecure install methods.

  13. A question for Clem: Is there a way to set a limit on memory usage in LM 20.3? My observation has been that the longer you let your system run, the more memory it uses…

    So far I have yet to see it go above 7GB but when I do a fresh boot everything is fine and running with 1.2GB.

    Please explain why your OS is doing this? Thanks, Ken

    1. If it’s about memory usage by Firefox about:performance in the search bar will show you everything.
      If it’s about LM, try System Monitor/Process or find a better place for that question – in the dedicated blog entry for your LM version and DE maybe

    2. “find a better place for that question –… Does that mean: ” “get lost and don’t bother us here?”
      Are you saying that this is an irrelevant or trivial question? I’m not sure of what it is that you are trying to tell me.

    3. For an example: I started a LM session this morning and checked the memory usage… 1.2GB. I did some web browsing and the closed all the open programs and put the computer in “suspend” mode and went off for about 2-3 hours. I just came back and woke the computer up and checked the MU… 2.5GB. This is after doing nothing and I do not use Firefox, I use the Vivaldi browser. So the longer the computer runs with LM, regardless if it is being used or not, the memory usage continues to increase for no apparent reason that I can see.

    4. What DebbieFan probably wanted to make clear is what Clem stated in the blogpost:
      ‘The comments section on this post is exclusively dedicated to support. If you have questions, or you need help about the technical aspects of this transition then this is the right place.’
      ‘For any other topics use the forums or the other posts on this blog.’

      So: Firefox transition only… No one tells you to get lost. Please stop making those harsh assumptions and read the post completely.

  14. Since the transition, the German dictionary is missing. The spell checker only works for the English language. I use Linux Mint 20.3 Cinnamon, currently with Firefox 95.01.
    dpkg -l firefox* says that “firefox-locale-de” is installed in version 95.0.1+linuxmint3+una.
    In the Firefox settings “german” is selected as first language. What do I have to do to get the german spell checker back?

    1. Removing and then reinstalling the german language pack under Add-ons > Languages helped. Is this the right way to do it, or does this ignore the package manager language packs?

    2. Hi Jakob,

      In a text area (any website where you’d write something, a comment here in this section for instance), right-click an empty zone and select Languages -> Add Dictionary.

  15. Hi Clem,

    all right, from there I also reinstalled the language pack. The correct dictionary appears automatically as an Add-on after that. Thanks.

  16. can i still have a different browser as the default browser as i don’t use Firefox as my main browser, my preference is pale-moon.

    1. Yes absolutely, you can have any browser as default. This is set by your desktop environment. For instance in Cinnamon you’d set that in “Preferred Applications”.

    2. the reason i asked is i have set pale moon as default browser, but when i select shortcut on my desktop to eldersweather.com.au , it opens firefox instead of palemoon, does anyone know why as palemoon is my prefered browser

    3. hi Clem it uses Firefox in the exec file, so that has enabled me to fix the problem, thankyou very much, by the way i find 20.3 great, thanks to you and the team for an excellent job πŸ™‚

  17. Will I still continue to get advice about my Linux mint version? Is so useful the start screen that advice you to change to a newer Mint version when the long term support expire?

    1. You can set a custom URL for the home page in Settings -> Home -> New Windows and tabs. The URL was previously set to https://www.linuxmint.com/start/una (where una was the codename for your Linux Mint release).

      You don’t need to rely on this URL for EOL and new versions though. In recent versions of Linux Mint the system reports check this for you.

    2. I use “https://blog.linuxmint.com/” for my home screen to get the latest on all things Mint.

  18. Suspect this is a non-event.
    Installed Firefox into LMDE4 today and it retained every single customisation.
    In addition, I was able to remove English-CA (whatever that is).

  19. Upgraded – No issues.
    All previous settings retained.
    Thanks Clem much appreciate all the work you and the team have put in on this.

  20. Downloading the update from the official Mint repo was pretty slow, but other than that the process was smooth (Mint 20.3). Firefox looks pretty much the same as on other platforms, but that was the goal of Mozilla, to keep the identity of the browser. The rounded corners are perfect now, yay!
    Thanks for the detailed explanation regarding the profile settings backup, I’m sure it will be useful for many people.
    Thank you as well for the hard work you put into the development of Mint, you’re always doing a really great job!

  21. Upgraded to FF 96 with no problems or configuration changes.
    PS. The only problem is that FF blocked Reddit… but other than that no problem in Mint

  22. I appreciate all the details being written out here on how to make a backup.

    I just updated and noted that the telemetry was re-enabled. I intentionally set telemetry to disabled, but this update apparently does not respect that setting.

    I think there should be a warning (not only here but also in the OS) that the telemetry settings are not respected.

    1. Hi Patrick,

      There’s an explanation as to why that happens in this transition. Note also that Firefox puts an infobar (“Choose what you share” or something like this) so that you review the settings and set them to your liking.

  23. Why not just direct people to the Linux Mint forum instead of here to discuss this issue? There is a different barrier to post in there as opposed to in the blog comments but the majority of users having problems will not likely come here to see if there’s someone with their problems nor is it easily findable via search engines unlike for what’s available in the forums. Just a suggestion… it would be easier that way to also manage the off-topic tangents. My 2 cents.

  24. Why restoren the file prefs.js is not mentionened in the blog post to get back my personal settings after update?
    I wonder if I am the only one, but after update to FF96 indeed ALL of my custom settings vanished (incl. all settings made via about:preferences as well as via about:config). Good thing was, that I just had to restore the freshly generated/virgin file **prefs.js** by an version before the update (either made by manual backup/copy of profile folder or directly within the current profile where FF automatically keeps all prefs.js backups and simply name the correct version (for me biggest filesize + newest date) and rename it e.g. from prefs-46.js to prefs.js).

    I wonder, why this is not mentioned in the blog post – maybe you should mention this too?
    In comparison I did not found an chrom/user.css I needed to replace.
    Cheers, Robert

    1. My guess what you did being neither recommended nor mentionned is because you probably did the most horrible thing possible : running FF96 with a FF95 config file.
      Prefs.js is much more than a tweak file for custom settings. They are indeed a part of it, but not the only part.
      One example to make you understand with those FF96 prefs :
      user_pref(“distribution.iniFile.exists.appversion”, “96.0”);
      user_pref(“extensions.lastAppVersion”, “96.0”);
      user_pref(“extensions.lastPlatformVersion”, “96.0”);
      user_pref(“extensions.databaseSchema”, 34);
      user_pref(“extensions.lastAppVersion”, “96.0”);
      user_pref(“extensions.lastPlatformVersion”, “96.0”);
      and yours which probably are one minus if you plugged an FF95 prefs.js (95.0 and 33)
      This means you’re sending false infos about your version to everything that interacts with FF.You may run into trouble one day or won’t be able to upgrade adds, extensions or FF itself because you’re basically telling you run another version.

      The correct way to do things is, as notified by Mozilla in the header of all prefs.js files :
      // To change a preference value, you can either:
      // – modify it via the UI (e.g. via about:config in the browser); or
      // – set it within a user.js file in your profile.

      If you have lots of custom settings and find it boring to manually set them through about:config, you should invest some time to understand how a user.js file works. I’ve about 300 prefs in my user.js, none was altered during the upgrade process and my version values match my FF version.

  25. Starting Firefox with a blank Start Page takes 3 seconds.
    Starting Chromium with a blank Start Page takes < 1 second.
    This delay seems to be larger than before with older Firefox versions.
    Can anyone confirm this observation?
    Is there a way to speed up the Firefox start?

  26. Updated FF on LM-20.1. Can’t replace mint-Y title bar (large red close button?) for FF. Does not match the system theme, currently mint-y blue old style (small blue close button), the only version of mint-y installed. Firefox declared itself default browser in FF settings. Clicked on a link and it opened in Vivaldi per ‘preferred applications’ setting.
    Neither of these happened on my test box, updated to 20.3 from 20.1 prior to FF update. Everything else, on both, seems to work as expected.

  27. Downloading the update to Firefox 96.0 on January 14th was extremely slow. I thought it might just be a temporary anomaly.

    But the update to 96.0.1 today was also extremely, ridiculously slow — less than one-tenth of the download rate I normally get!

    I used the default mirrors both times.

    Is this a known issue that will be resolved soon?

    1. Hi Tom,

      I think it’s because of the recent 20.3 release and upgrade. Switch to a local mirror you’ll get better speeds.

  28. I have been attempting to get Mozilla to enable me not to use the enterprise version of Firefox 96, since it was installed. Turns out, Mint is the source of my problems not Firefox. I have been spending most of my time trying to repair the damage resulting from the Firefox update.

    Firefox has told me that my problems were created by MINT, and this page confirms that.

    I am using Tara 19. My experience with Ubuntu taught me not to update my os to new versions regularly. I have avoided updating from Tara, for the reasons I moved from Microsoft to Ubuntu, to Mint, every update creates a less functional system. For example, from Windows XP to Vista, etc. My wife’s machine Windows 10, and I hate having to maintain it since it becomes more moronic every time I look at it.

    Now you are telling me that Mint has decided to force Mint users to use Google rather than DuckDuckGo, thus facilitating tracking, spying, and identity theft. No way!

    I suppose updating to your newer version of Mint is one solution, but this article tells me that that equates to updating from XP to Vista.

    How can I restore my current version of Mint to the stable version it used to be before you latest meddling?

    I maintain my system, and I want to reverse you changes discussed in this article. How can I do that?

    1. “Firefox has told me that my problems were created by MINT, and this page confirms that.”

      This update actually cancels Mint changes, thus making Firefox the same as it is in other distributions and operating systems.

      “Now you are telling me that Mint has decided to force Mint users to use Google”


      “I want to reverse you changes”

      Restore personal backups to ~/.mozilla and your latest Timeshift system snapshot.

  29. Thank you, Clem, for your recommendations about to backup FF profiles and to make a system snapshot. I have not more issue than absence of spelling dictionary… Coincidentally, there were an electrical interruption and my FF profile was damaged and now backup is useful to everyone for reestablish browser in case of an incident. Thanks a lot!

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