You cannot downgrade Firefox 55 profiles

Martin Brinkmann
Aug 2, 2017
Updated • Aug 3, 2017

If you have upgraded a version of Firefox to version 55 or newer, you won't be able to downgrade that version of the browser later on to an older version.

While Mozilla never really supported downgrades of the browser before, it was usually no problem to downgrade a particular version of the Firefox browser.

There are two main use cases where this happens: first, when a release version of Firefox causes issues, and when users use the same profile on different versions of the browser.

The first issue happens when Firefox users run into issues after an update of the Firefox browser. They may then install the older version of Firefox anew. Since Firefox picks up the default profile automatically, or another profile if you point it to it, it may be used automatically by the browser.

This can lead to some issues regarding the profile, as new versions of the browser may introduce new features or change some. The effect may be noticeable on the older version, but it usually won't cause the browser to stop working completely.

The second issue happens when you use different Firefox versions using the same profile. This is not advised as you may run into the same issues described above (as you switch between different release versions).

A bug report on Bugzilla@Mozilla highlights that profiles of Firefox 55 or newer won't work in older versions of the browser anymore.

Firefox 55 is the next release version of the browser; the planned release date is August 8, 2017. While the information is useful in itself, it is especially important for users who plan to move to Firefox 52.x ESR when Firefox 57 gets released in November as the profile won't work then anymore if they have installed Firefox 55, 56 or 57 at one point in time.

In short: If you want to switch to ESR, it may be a good time to do so before the Firefox 55 release. You may alternatively create a backup of the Firefox profile before you upgrade to Firefox 55, and restore it after you install Firefox ESR on your system.

Mozilla notes that the organization changed the "on-disk format of persistent storage in profiles" in Firefox 55, and that this change is the reason why you cannot downgrade to an earlier version of Firefox after you used the profile on Firefox 55 or newer.

Once a profile has been used with Firefox 55 (or later), it should not be used with previous versions of Firefox. IndexedDB, the (DOM) Cache API, Service Workers, and the asm.js cache will all fail to operate, generating confusing errors and causing portions of Firefox and some websites to break. The profile can be made operable again in older versions of Firefox by using the profile "refresh" mechanism.


You cannot downgrade Firefox 55 profiles
Article Name
You cannot downgrade Firefox 55 profiles
If you have upgraded a version of Firefox to version 55 or newer, you won't be able to downgrade that version of the browser later on to an older version.
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  1. Migrating to K-Meleon said on August 18, 2017 at 3:17 pm

    So, If I use portable FF, how do i roll back since John Haller doesn’t port the ESRs.

    Copy, save current profile, then paste into an older copy [from fileHippo] then grab the ESR from the main channel? Used to do that years ago when portable updates were a lot slower that desktop updates and everthing still worked. Really can’t remember how I did it, so long ago.

  2. A41202813GMAIL said on August 5, 2017 at 4:41 pm

    I Will Stay With FF5101 – Even The 52ESR Version Is Incompatible With Some Prior Extensions.


    1. TimH said on August 6, 2017 at 6:35 am

      I Think You Mean InitialCap-ocalypse Forever

      1. A41202813GMAIL said on August 7, 2017 at 1:09 am

        It Is Just The Output Of A CHROME Extension.

        If You Do Not Agree With Me Just Say So, And Stop Pretending You Are A Spell Check Cop.


  3. Mark Hazard said on August 4, 2017 at 2:36 pm

    Is it legal to switch to the ESR version if you are not an organization? Just asking. I am thinking of switching but am put off by the warnings on the download page.

    1. Tom Hawack said on August 4, 2017 at 6:53 pm

      It is legal. I run Firefox ESR, many users do. Forget the warnings.
      Direct downloads available at Mozilla Firefox release directory [], all ESR versions are of the form %VERSION%esr/

      1. Mark Hazard said on August 5, 2017 at 6:36 am

        Thank you for replying, I will try the ESR version.

  4. Thorkhan said on August 3, 2017 at 10:58 pm

    “Beware & prepare!” – the way to handle Mozillas stupid decisions. Thanks for warning! :)

  5. John T. Haller said on August 3, 2017 at 9:52 pm

    If you ever want to try a Nightly (or Dev or Beta) build of Firefox without it affecting your local installed version, you can grab the portable version from Firefox Portable Nightly is currently at version 57 and will download the most recent 32-bit and 64-bit builds as you install.

    1. The Dude said on August 5, 2017 at 2:16 pm

      Duuuude! Google got nothing on you. How would we manage to live without Pants?
      A little chilli and with boners I guess.

    2. stilofilos said on August 4, 2017 at 12:45 pm

      A few years back, I tried such a PortableApps one, and noticed that it launched the usual Firefox, creating the hundreds of registry items it ‘needs’ for working. (I had uninstalled FF before and cleaned the registry out…)
      I mentioned it on a forum like this one, and people replied that they just call it ‘portable’ cos it deletes those registry items when you close your session. Theoretically then, cos I had noticed the issue exactly because they were still there after that…
      No idea whether it’s still the same, but why and how would they have changed that meanwhile… ?
      So, ‘without it affecting your local installed version’…, You might be lucky, but I would not be too sure about that. Be careful !

      1. Pants said on August 4, 2017 at 8:31 pm

        “Portable” means that everything needed to run the software is all within the directory (eg D:\FirefoxPortable\”). And if you move it anywhere (eg M:\FirefoxPortable\” – a usb stick), it will still run – as it uses relative paths (i.e relative to the exe). Some portable software packages may require dependencies (eg runtimes or .net).

        “Stealth” refers to not leaving any traces outside the directory (excluding temp files), such as registry entries and %appdata%

        Portable FF does not create any registry entries that I know of (maybe a background installer item, not 100% sure). The only ones in my registry are those for file association/default browser. And I’ve been on the portable FF train for 4 or 5 years.

  6. TelV said on August 3, 2017 at 4:05 pm

    Second thoughts, in the light of this article I decided not to wait until FF57 has been released and switched to Firefox ESR (52.2.1) about an hour ago.

    Also, an article on Github concerning Classic Theme Restorer was instrumental in persuading me to make the change earlier than intended:

    So far, no adverse effects.

  7. The Dude said on August 3, 2017 at 3:24 pm

    wowowo… hold your horses will’ya?
    We ain’t heard from Pants yet. He’s the Sheriff.
    We gotta wait for Pants and his comments.
    He is the master. Not even Chuck Norris can outsmart him.

    1. TimH said on August 3, 2017 at 11:27 pm

      Getting help from Pants will possibly be more likely if you get her gender right…

      1. Anonymous said on August 4, 2017 at 12:38 am

        Pants have no gender, they are empty inside.

    2. Tom Hawack said on August 3, 2017 at 3:50 pm

      “I shot the sheriff
      But I didn’t shoot no deputy, oh no! Oh!
      I shot the sheriff
      But I didn’t shoot no deputy, ooh, ooh, oo-ooh.”

      That’s what the song says. If he ain’t dead someone get him alive.
      He’s likely busy on his Github-Ghacks-User.js pages. If I go there I’ll tell him he’s wanted in town, people want him, he’s acclaimed. Pants for president.

  8. Nik said on August 3, 2017 at 1:29 pm

    Why is this post under uncategorized?

  9. TelV said on August 3, 2017 at 12:39 pm


    The recommendation on Mozillazine is to use the BETA version of the Mozbackup utility which is 1.5.2 Beta 1 since the normal release sometimes doesn’t backup everything it’s supposed to apparently. See:

    Personally though, I prefer the old fashioned copy/paste method which is much more reliable than relying on third party backup utilities.

  10. Nik said on August 3, 2017 at 7:16 am

    Changed to ESR version. IDM integration module is not supported. :X

    1. Nik said on August 3, 2017 at 3:32 pm

      Update – IDM does supports Firefox 52 ESR. Just need to install extension manually.

  11. Dwight Stegall said on August 3, 2017 at 4:04 am

    I wonder if Firefox 55+ will work with Mozbackup?

    1. Dave Johnson said on August 15, 2018 at 10:25 pm

      That’s a good thought – yes I know this is a museum piece thread! – but the writers of mozbackup could do the world a real favour here if they begin using an application-specific and version independant mode of storage for the backed up settings.. Then it would become a real liferaft for the victims of mozilla’s latest sneaky trap.

      After the firefox trapdoor’s been closed for a while more and more users will realise that a chrome-clone is no benefit compared to the multitude of lovely tweaks and boosts that were available via the true addon system.

  12. TRoy said on August 3, 2017 at 3:39 am

    I updated to the RC1 yesterday and found a few things that I did not like. I re downloaded the 54.0.1 64bit and installed over 55 rc1 64bit and was able to use my profile both before and after the downgrade without issues so far. in fact I ran into no issues after installing 55 over 54.0.1 and no issues after installing the 54.01 over the 55rc and using the same profile.

  13. Earl said on August 3, 2017 at 12:34 am

    Every time I updated from x to x+1, I’d always copy x to y and then update y–always leaving x as a way to backout to where I was before the update. (Of course, you could just use typical backup/restore as well.)

    Plan for failure–or, at least, some incompatibility. (And, yes, I do still have every older install available on one computer or another.)

  14. Tom Hawack said on August 3, 2017 at 12:20 am

    This is why downgrading Firefox must imperatively be accompanied with the latest profile backed-up before the browser had been upgraded.

    I backup my Firefox profile systematically, regularly, always before installing a new add-on, and if there’s one situation where that profile backup is really required it is before upgrading Firefox. Name the backup ‘Last_FF_X’ with X as the Firefox version, upgrade. If there’s a problem then or later on, uninstall Firefox, restore the saved backup X and install previous Firefox X. Clean installs have my preference and take my decision always if downgrading (I clean upgrade as well).

    Of course techies might say this is as a clean way of proceeding as a newbie’s ignorance, but basic methodology, if a handicap when it comes to imagination and creativity, remains a saver when organization is concerned. Chaotic cupboards or attics are charming, excess of order is a poison for a wealthy soul …. but when computers are concerned, have a method, use it.

    Backup, backup, backup.

  15. Bobby Phoenix said on August 3, 2017 at 12:18 am

    This happened to me recently. I was on the stable channel, and decided to try the nightly builds. Didn’t really care to stay, so I uninstalled it, and tried to go back to the stable channel. A bunch of headaches later the only solution was the refresh. Maybe they should’ve put that warning out there when you download a version of 55 or later.

  16. Yelan said on August 2, 2017 at 11:30 pm

    Trying to lock in current users?

    I mean… it’s going to be released “on the quiet”:
    “I don’t think Firefox has ever supported moving profiles from a newer version to an older (i.e. using a profile created in 55 with, say, 53 or 54). So, a release note doesn’t seem necessary.”

    1. Anonymous said on August 3, 2017 at 8:03 am

      It’s not quiet, it is literally written in Firefox 55 release notes.

      Besides, such a method makes zero sense if you want to “lock in users”.

      1. Anonymous said on August 3, 2017 at 9:19 am

        > such a method makes zero sense if you want to “lock in users”.

        Making sure people can’t downgrade or switch to an ESR version or alternative Firefox-derivative browser without data loss means locking them in, in my book. Or at the very least making things extremely inconvenient/not something people want to deal with. No backups are made, either. You run FF55+ once and that’s it, no way to recover your data intact.

  17. Richard Allen said on August 2, 2017 at 10:43 pm

    This last weekend I updated v54 to 55 Beta for a couple days. Luckily I knew to save a copy of my v54 profile folder and actually remembered to do so and was able to reinstall v54 without any problems. After the update to v55, the about:config entry ‘privacy.resistFingerprinting’ needed to have the width and height set, on 54 I could use it by itself with no issue. That was kind of annoying.

    And… Nightly updated to v57 earlier today and it is still running one Legacy add-on. For now. I doubt if that lasts more than a day or two.

  18. Anonymous said on August 2, 2017 at 10:32 pm

    Wow thanks for the info! Time for me to switch to the ESR version like I already installed on all my friends’ computers.

    1. Tom Hawack said on August 3, 2017 at 12:23 am

      If you do switch to the ESR version do take into account ESR is a FF52. Take care should you downgrade from a Firefox 53+ to FF ESR 52. But you must know that already.

      1. Anonymous said on August 3, 2017 at 1:20 am

        Thanks, I have backups in the fridge. Anyway I will switch to Pale Moon as default browser and keep Firefox as portable for few sites I use rarely, not working with it, like one showing a blank page and saying “Uh-oh…”. Finally I’m getting tired of all that “cirque” which has been going on for too long.

  19. RPWheeler said on August 2, 2017 at 10:28 pm

    I wonder if there is anything in Firefox Mozilla is NOT going to make worse.

    1. Not A Sheeple said on August 11, 2017 at 6:30 pm

      Its people like you who started it in the first place.

      People started complaining that Firefox is not keeping up with Chrome and Mozilla has no option other to start racing with Chrome and keep bumping the version number mindlessly as Google did with Chrome, so that you people can get hyped that an update is available.

      The issue is with the end users who don’t understand what Open Source is and who have no idea that there is a thing called Privacy when using a free product.

      There is a term called “If you are not paying for a product, then you **are** the product”. Maybe you should read this,

      Firefox v2 is/was the best Firefox I’ve ever used and Firefox became worse & worse leading to decline in its market share because of people complaining like you.

      People like you don’t understand the scale of the code in the Firefox project and maintaining it is not an easy task.

      I guess Mozilla learned the lesson that they should “stop listening to the complains of complainers who complain about everything” and focus on constructive feedback & bug reports.

      Q: Have you ever filed a bug report? or do you even know what it is?

      PS2: Using Firefox since v1 and Firefox 55 is the best release since then IMHO. Kudos & Respect to Mozilla & everyone involved in this huge project.

      1. AAA said on December 15, 2021 at 10:09 am

        firefox became bloatware. 550 version in just 3 years For what ???

    2. AnalMan said on August 5, 2017 at 8:36 pm

      fracking right! the only reason im not erasing FF from all my pc is the multi row tab addon tab mix plus

    3. ams said on August 3, 2017 at 4:32 pm

      The “RPWheeler” attempted trolling comment contains a poorly worded question/statement. IMO it should be deleted, along with the replies it has generated (including mine).

    4. Tom Hawack said on August 3, 2017 at 1:13 pm

      Emphasizing on fans, fanboys is somewhat a fan attitude.
      Of course fans exist, everywhere, a way maybe to trigger enthusiasm for the best, a complex of superiority for the worst, most of the time to believe that one belongs, by his devotion, to a group of winners.

      People love stars, as fanatics sometimes. Hence, fans, fanboys.

      Choosing may also correspond to what we believe to be, if not the best, at least not the worst. Nothing is perfect, browsers included. I think, I guess (no stats!) that most users who have interest for computing, who test several browsers, who as such have a background of factual experiences… well, opt for one browser rather than for another without being led my fanaticism, sectarianism.

      I don’t know what is the best browser, I don’t even know what criteria should be considered to lay such an omnipotent certitude. I just know the browser which fits the best for me (yes, sometimes excluding the masses can help objectivity) at a given time corresponding to my expectations at that time. Now it’s Firefox. We’re not married, if I find happiness elsewhere I’ll just pack my stuff and move on. Never say never, right?

      1. Tom Hawack said on August 4, 2017 at 9:51 am

        @Anonymous, that smile I detect within your wording seems to me very French :)
        Yes, clichés, stereotypes. Especially nowadays where people move around so much, with their culture in their luggage, there’s more and more melting and it’s never been tougher to characterize a nation’s identity, even if specifics remain. I’d say that anyone who travels, who has traveled, is on the path to a planetary “citizenship”.

        Concerning Firefox, I just don’t know what she knows of me… and I don’t want to know. Secret gardens are valuable :)

      2. Anonymous said on August 4, 2017 at 12:37 am

        There’s a stereotype going on about the French: They don’t attach the same value to marriage and fidelity than say, the Americans.

        ” Why not a liar as well?! ”

        Well, does Firefox knows that at some points during your long term relationship, you have been visiting another browser nightly ? Does she ???

      3. Tom Hawack said on August 3, 2017 at 6:17 pm

        I appreciate your concern, Anonymous!
        Not sure what French have to do with being married or not!
        So, you believe I’m a bachelor, an adventurer moving from one cellar to one castle, from a flat to a duplex, accompanied by my computing devices, a red-line with the NsA, a pure geek, an arguable correspondent?
        Why not a liar as well?!

      4. Anonymous said on August 3, 2017 at 3:58 pm

        You are such a French, not married after so many years, ready to pack your stuff at any time, heck, I’m sure you even installed a couple other browsers in your time with Firefox!

    5. Harushi said on August 3, 2017 at 11:25 am

      Your opinion

      1. Anonymous said on August 4, 2017 at 12:15 pm

        Ok I’ll spill the beans before someone ricks a finger typing some huge essay carefully explaining how everything is shit.

        “Your opinion” is what Firefox Mozilla is NOT going to make worse.

      2. RPWheeler said on August 4, 2017 at 10:01 am

        This is opinion of active PC user since 1991, software tester since 2008, Web browser user since 1999 and Firefox active user since 2007.

        1) I cannot name any big improvement in Firefox since Firefox 3
        2) I saw several (4, I think) notices of the authors of add-ons I use about stopping developing develop them because of “web-extensions” move (and heard that there is more for add-ons I don’t use).
        3) I can’t name any Chrome-like “web-extensions” advantage over Firefox XUL ones.
        4) It’s not just me who had to downgrade something at some point of time because of some issues. If downgrade itself could become source of issues, it’s never for better.
        5) At my home PC I switched back to Pale Moon and it is just faster.

        “Improvements” may be my opinion, but as for add-ons stopping being developed it is not. Functionality of add-ons also might be compared. SO far I heard only about restrictions, but not about any new possibilities.

        How can it be better if you want all your stuff continue to work, just faster?

      3. Anonymous said on August 3, 2017 at 3:56 pm

        Sounds like someone didn’t parse two words properly

      4. @Anonymous @Harushi said on August 3, 2017 at 12:45 pm

        Not just his opinion. The decline in the Firefox’s user base is a clear indicator. You fanboys will never learn, it’s not just about Google doing it right (they are NOT that good), it’s about Mozilla doing it wrong also.

    6. Anonymous said on August 3, 2017 at 12:15 am

      Your opinion

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