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I cannot get thunderbird to run on my computer (it runs fine on my wife's computer). I keep getting the profile can't be loaded error. I have tried the fixes recommend here but none worked.

Hello,

In my Thunderbird Profiles folder, I can drill down to ImapMail. I see multiple subfolders prefixed with my imap server name. eg:

- imap.server-5.com 10.85GB - imap.server-3.com 8.83 GB

and so on. The datestamp on each is different.

Within the two examples above is a large Inbox folder taking up ~8.8GB.

The size doesn't concern me as much as the fact of having two of these. I'd like to understand what Thunderbird is doing under the hood here. Does it create new imap.server-#.com folders periodically as backup/recovery folders?

I'd like to recover space where possible but if these are protective measures, I could live with that. However, if it creates future folders and replicates 8+GB of data multiple times, I'd like to know what steps I can take to free up disk space.

Thanks,

I had a problem where FF 140.0 would not update, and in trying to get FF yo update, I used a re-install tool to which I was pointed in my problem report. This caused FF to wipe out my configuration, and I lost all my windows and tabs. I have gone to

    \Appdata\Roaming\Mozilla\Firefox\Proifiles\abnfpged.default

cleared all of the data therein, and restored that directory from a backup I made last Monday. But I cannot get FF to use that directory. "about:profiles" shows only two profiles, but the Profiles directory has five profiles:

03/10/2026 09:39 AM <DIR> qf00ka5x.default 03/10/2026 09:39 AM <DIR> v842ceue.default-release 04/11/2026 09:16 PM <DIR> .. 04/11/2026 09:16 PM <DIR> . 04/12/2026 03:08 PM <DIR> abnfpged.default 04/12/2026 06:29 PM <DIR> jdfj91sd.default-release-1775960183850 04/12/2026 06:48 PM <DIR> f1jq4mlq.default

Only the profiles beginning with "j" and "f1" are seen in the "about:profiles" screenshot I have attached. And I have attached a screenshot of my profiles.ini file. Also, in the abnfpged.default directory I restored, where is the list of all of my open windows and tabs? FF used to keep that in a sessionstore.jsonlz4 file, but that file is only written when FF closes. I tried to save a copy when I was having problems, but I stored the copy in the same directory, which FF changed during the re-install process. Here is my profiles,.ini file:

[Install308046B0AF4A39CB] Default=Profiles/jdfj91sd.default-release-1775960183850 Locked=1

[Profile1] Name=default IsRelative=1 Path=Profiles/f1jq4mlq.default

[Profile0] Name=default-release IsRelative=1 Path=Profiles/jdfj91sd.default-release-1775960183850

[Install641D10338ABA448D] Default=Profiles/abnfpged.default Default=1 IsRelative=1 Locked=1

[General]

StartWithLastProfile=1

Version=2

[BackgroundTasksProfiles] MozillaBackgroundTask-308046B0AF4A39CB-defaultagent=lnvi5jn5.MozillaBackgroundTask-308046B0AF4A39CB-defaultagent

I have not worked with the ;profiles.ini file in many years, as my FF configuration has not had problems. Thanks.

Have been using the 104.9.0esr 64-bit release on Windows 11 for some time now (mostly for email, involving a number of email accounts) and have been generally satisfied...

...but discovered when I started looking into switching over to the 145 default release that I have a capital-P Problem. The first thing recommended on making that change is - sensibly - to back up one's Thunderbird profile. Only as far as I can tell, I don't *have* any such file anywhere on my system. [To answer the obvious question - yes, I've got "View" set in File Explorer such that it should be showing me hidden files.]

I have drilled downward through all the USERS subdirectories on my C: drive. "Default" and "Public" have nothing at all (as one might expect). My personal subdirectory has a Mozilla directory under "Roaming", and both a Firefox and a Thunderbird directory therein, but the only things in the Thunderbird directory are an empty folder labeled "Crash Reports" and a tiny "desktop.ini" file.

There is a "Mozilla Firefox" directory under Program Files, but nothing in that hierarchy looks applicable. There is a "Mozilla Maintenance Service" directory under "Program Files (x86)", but nothing there appears relevant. There is a "Mozilla [alpahnumeric hash]" subdirectory under "Program Data", but nothing there appears relevant.

And in fact, I begin to think I have a bigger issue than I thought I did...because the more I poke at my C: drive, the less I'm seeing...to the extent that I'm not at all sure where the Thunderbird program itself (not to mention a quite large accumulation of associated email) is being kept.

Which would be nice to know if one were attempting to back up one's mail before changing program versions....

I have been using Firefox profiles for years, long before the announcement of the new profiles UI. The new profiles UI launhed with FF 144. I'm on the latest version, which is 149.0.2 and I still don't have the new UI. Specifically, I do not see my profiles in the new UI.

When FF launches I see the new UI but my profiles are nowhere to be see as you can see in the screenshots:

https://postimg.cc/gallery/tFXz00m

I have 2 profiles and they each have their own name.

Instead I am presented with 2 option "Original Profile" and "create new Profile". When I click on orignal profile, Firefox opens my default profiles which has its own original name. However, when go throught the new UI o switch profiles, I do not see my other profile. Moreover, if I click manage profiles, I don't see either of my profiles.

The only way I am able to launch my 2nd profile is the old fashiong via "about:profiles".

Why can't I see my profiles in the new UI?

On my 2nd profile, I don't even have the new profiles UI.

Why dont't I have the new profiles UI months after you launched it?

Please help!

A windows update occurred this AM 04/15/26 and it has affected my browsing. Don't know if this update effected my G mail. My U tube profile changed form browsing to history. example: when I click on to my U tube profile it brings up the last view I was browsing. I cannot refresh Firefox like before from the help menu, of which would select the profile I desire.

Thunderbird installed a new version and would not open until I created a new profile. Now all my locally saved email is missing. The only profile I can find is the new one for my email account, dated April 2026. Where is the old profile with all my saved emails? I have no email older than April 2026 in my Inbox. POP3 email, saved to my desktop computer, is gone. Please help me find them.

I did the profile thing and there's only one blank profile showing.

I did the CMD prompt -P and there is only Default showing.

This new upgrade has destroyed everything

I'm trying to understand Profiles, especially since I am transitioning to a new laptop.

On my older machine, I have an Original Profile. Since I've never specifically created a profile, I assume that Original Profile contains my current Settings, Bookmarks, etc. Is that a correct assumption?

My new machine also has an Original Profile. Do I need to copy my Original Profile from my older machine to the newer machine? Should I rename the profile on the new machine or leave it as Original Profile?

I recently set up an ex-Win10 PC as a Linux media player and was delighted it came with Firefox. I created a separate profile on my Win11 PC for use on the media PC. In this profile I have a few stored bookmarks, log on IDs * passwords, for sites such as BBC iplayer etc.

I did eventually manage to load it on the media PC but when I went back to my Win11 PC I couldn't find my original Firefox account. When I tried to switch accounts, it wanted to load all my original bookmarks etc and combine them in the new profile.

It's now evident that I didn't realise the difference between accounts and profiles (and I'm still somewhat confused). I can't find any clear help on how to switch between accounts and profiles. Why am I finding it so difficult? Perhaps Firefox is being too smart for me.

I used Firefox this morning and it worked normal. This evening however it will not open as normal. It appears to want me to create a new profile. It does not have a toolbar or any of my bookmarks What do I need to do to restore

First off - love Mozilla's work, thank you all for your efforts!

The problem: I f'd up with the Profiles option. I wanted to set up a Work profile on a new windows laptop associated with a new work email (msta....), and then separately have my personal profile connected to my gmail (mstn...).

Well somehow I managed to make my Work (default) profile connected to my overall Firefox + Google personal profile, and have spent a month in my ignorance saving away settings and bookmarks on this machine. Is there anyway that I can disconnect my Gmail account from the profile Work, and connect it to the secondary profile on the same machine titled 'Mel'? Or will I need to export the last month of bookmarks, implode my Mozilla install on this machine, and start over with new profiles and better practices?

Help, multipass!

Thanks, Mel

MacOS 15.5

I accidentally deleted my Firefox profile not knowing its criticality. When trying to open Firefox, I receive "Profile Missing. You're Firefox profile cannot be loaded. It may be missing or inaccessible.".

1. I have uninstalled and reinstalled Firefox to no success 2. In the Library/Application Support directory, there is no Firefox or Mozilla folder 3. In the Library/Caches directory, there is no Firefox or Mozilla folder 4. I have tried opening Firefox by pressing option + click, no change in behaviour

Hi, I am hoping that the community can help me find an answer to this. I have two computers that I use for work. The one in the office has TB running all the time and before I leave for the weekend/vacation I would close TB, copy the profile folder to a USB (or copy it to cloud) and then paste the profile folder on my work laptop (at home). While all the settings get copied (local folders structure, addons etc.) as I use IMAP, it downloads all the mail on the new system regardless. I thought that it should have the latest mail downloaded as part of the profile folder, is that not the case? The bigger issue is that none of the Completed Tasks Lists, Templates, etc. get updated. It still shows all the older stuff on the work laptop and no updates carry over from the PC (at work). Going through the profile folder I see multiple copies of the files prefs.js, folderCache.json, global-messages-db.sqlite appended as: prefs-computername.js and folderCache-computername.json etc. (The computername is the name of the PC - office/laptop) The profile name is the same between the two computers. TB is only started after the profile is copied locally. TB version is the same between systems. I am left scratching my head why somethings are copied but not others. Hoping that the community can help me here. Thanks!

WHAT THE HELL IS MOZILLA DOING?!?! THEY KICKED ME OFF MY PROFILES AND PUT ME ON A DELETED ACCOUNT. I've been asking for one month and no one ever responded. This company is trash and wont even provide support for their mistakes. Some even replied to me making fun of my situation... The worst service I have experienced....

Hi,

My Firefox had auto updated to the newer version with AI built-in and auto-enabled, which meant the browser would crash EVERY. SINGLE. TIME. I would launch it.

For perspective, I am running an old Lenovo Thinkcentre mini PC with an Intel i5 6th gen and 16gb of ram; its got Windows 11 installed, and always running out of memory with the simple things like browsing and word processing. This is NOT a PC or use-case that needs or warrants AI.

So, I uninstalled Firefox (149) and installed the latest version WITHOUT AI built-in (147).

I then synced my profile, and things ran fine. An hour passed, and then i kept getting an error, saying my profile was created with whatever and I need to create a new profile.

So, I created a new profile and synced, again, and I got the error, AGAIN...

I'm about to boycott Firefox on all the devices I control, and opt for an older version of Opera or something more obscure, so that I don't have to deal with this nonsense.

Hello! I just installed F-Fox yesterday and want to delete Google Chrome. However, my husband and I both used Chrome and I would like to add him to Firefox, so his history, passwords, etc can be imported but I don't know how to add his profile to Firefox along with mine.

Please help.

I have followed your instructions at https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer and gotten nowhere all day. on it. You have "Profile Folders", a folder called "Profiles", a bunch of profiles (folders) inside the Profiles folder and profiles in Roaming and in Local paths. When I get the old profile 'k41******' copied to the new computer in both the Roaming folder and the Local folder the Thunderbird program still will not show me the old files. I don't need any of the thousands of emails in the old computer, just the Templates in one account. This should be easy. I should just copy the profile k41***** ect. and paste it into the "Profiles" (notice the pleural there) and then Thunderbird should work. But it does not.

I got a popup when I opened a new window asking if I want to try out a build in VPN and I logged in to my Google account and after that it did a thing I wasn't expecting, it almost reset my browser but I left another Firefox window open and my data was still there and when I open Firefox my data wasn't there only my account which basally meant from guessing when I login to a Google account it created a completely new profile and mistaken it as the main one then hidden my old one to a point where I think it could get deleted if I close my old profile's window also because I checked profiles and there was only one on all the windows.

Oh and I was trying to export my browser data on the old profile but I didn't found a option, and I tried seeing what the sync feature does and I think when I actually added an account Firefox somehow changed it's mind and now thinks this is a different device or whatever because one of the things in the Connected Services says "Elbey (my username) Firefox on elbey" then another said "Firefox 149, Linux" which these two sound like my devices also because I tried out the sync feature on my old profile and needed to login and it actually worked without doing unexpected stuff which is also how I got this information.

No matter what I've tried, I cannot figure out a way to edit or delete the profile from the new profile manager. Both about:editprofile and about:deleteprofile show up as a blank page (with how it looks on my normal profile for comparison). I have tried deleting the folder multiple times, but the icon still shows up in the manager and clicking it just creates a new profile with the default settings. It also does not appear when using firefox.exe -p. I had previously been using the about:profiles to manage my profiles and wanted to see if I liked the new version (I didn't), hence why I was using it in the first place.) I'm currently using Firefox version 149.0 and Windows 11 on the latest version. I have found no solution that gets rid of it. I would also be fine getting rid of the profile manager UI so it stops bothering me.