Where apps hide your files

The Thunderbird profile folder

Updated 2026-10-28 · 6 min read

Thunderbird keeps all your mail, settings and address book in one profile folder under your Library. Here is how to open it, what is inside, and how to back it up or move it with Mozilla's own steps.

The location

~/Library/Thunderbird/Profiles/

Each profile is a folder inside it with an eight-character random prefix. Mozilla says a release or ESR install names its profile xxxxxxxx.default-release, and a folder ending in plain .default is normally an empty, unused dummy you can ignore (Beta and Daily use default-beta and default-daily). This is Mozilla's documented default for macOS; a profile made in another location is possible, which is what the next file is for.

~/Library/Thunderbird/profiles.ini

profiles.ini sits one level up and lists every profile and where it lives. Thunderbird is not installed on the Mac used for this guide, so the paths come from Mozilla's support article, and the same layout can be seen in Firefox's profile on that Mac (~/Library/Application Support/Firefox/Profiles/<random>.default-release, with installs.ini and profiles.ini beside it), which shares the profile design.

Open it from Thunderbird

This is the quickest route and it works even if you moved the profile:

1. In Thunderbird, choose Help > Troubleshooting Information (or the ≡ menu, then Help).
2. In the Application Basics section, find the Profile Folder row.
3. Click Show in Finder.

Open it without Thunderbird

Mozilla's route for a Mac that will not start Thunderbird: in Finder, click the Go menu, hold ⌥ and choose Library. Open Thunderbird, then Profiles. From Terminal:

open ~/Library/Thunderbird/Profiles

What is in a profile

Item	What it holds
Mail	Local folders and POP accounts
ImapMail	The local copy of each IMAP account, one subfolder per server
prefs.js	Your settings
abook.sqlite	The Personal Address Book
global-messages-db.sqlite	The Global Database search index; Mozilla says Thunderbird rebuilds it if you delete it with Thunderbird closed
*.msf	A small summary file for each mail folder
saved-password files	Mozilla says passwords live in the profile (as logins.json and key4.db, the same design as Firefox)

Do not email, upload or share a whole profile folder: it can contain your saved passwords and every message you have.

Mbox files: where the messages are

Messages are kept per folder. By default a folder is a single extensionless file named after it, such as Inbox, holding every message in that folder in the mbox format, with a matching Inbox.msf beside it. Mozilla's developer documentation calls the .msf a Mork database holding the header information for each message. Thunderbird also has an optional maildir format, set per account, which stores one file per message in a directory instead.

For a typical IMAP account the path to the Inbox is ImapMail/<server name>/INBOX. Because the mbox file has no extension, you cannot find it by file type. It is plain text holding whole messages, so treat any copy of it as private.

When you delete mail, an mbox folder does not shrink at once. Mozilla's developer notes say deleted messages stay in the file until the folder is compacted, so if Thunderbird's data is taking too much space, select a large folder and choose File > Compact Folder (or right-click it and choose Compact Folder) instead of deleting files by hand.

Back it up

Thunderbird's own route is its Export tool: ≡ > Tools > Export, then Export, and save the ZIP file it makes of your whole profile. Mozilla says it handles backups up to 2 GB; for a bigger profile, or without the tool, copy the folder by hand with Thunderbird closed:

1. Quit Thunderbird (⌘Q).
2. Open ~/Library/Thunderbird/Profiles/.
3. Hold ⌥ and drag your profile folder to an external drive or another folder, which copies it.

Keep the copy. Mozilla says a profile on cloud-synced storage should work in most cases, but it is not a backup, and opening the same profile from two running copies of Thunderbird (on two Macs, or one) is not supported and risks corruption and permanent data loss.

Restore or move it

Mozilla gives two cases.

If the backup folder has the same name, including the random characters, quit Thunderbird and replace the profile folder with the backup. If the names differ, or you are moving to a new location, open the Profile Manager, create a new profile where you want it, quit, then paste the backup's contents into the new profile folder and start Thunderbird.

With Thunderbird open, the about:profiles link on the Troubleshooting Information page manages profiles. To launch the Profile Manager with Thunderbird closed, Mozilla gives this Terminal command:

/Applications/Thunderbird.app/Contents/MacOS/thunderbird-bin -P

If Terminal says that file does not exist (Mozilla notes it may be missing on Sequoia), use:

/Applications/Thunderbird.app/Contents/MacOS/thunderbird -P

To point Thunderbird at a profile you have moved by hand, Mozilla says to edit profiles.ini. Quit Thunderbird, make a copy of profiles.ini, change the profile's Path= line to the new location, and set IsRelative=0 if the path is no longer relative. Save, then restart Thunderbird.

New Mac

Migration Assistant copies your Library, so it normally brings ~/Library/Thunderbird across. Mozilla's own method: make sure both Macs run the same, up-to-date Thunderbird, install it on the new Mac without opening it to check mail, then replace the new Mac's ~/Library/Thunderbird folder with a copy of the whole Thunderbird folder from the old one (not just the profile inside). The Export tool's ZIP, restored with Thunderbird's Import tool, is the other documented route.

Why a normal search misses it

~/Library is hidden in Finder, mbox files have no extension, and Spotlight and Finder searches leave out Library folders. Searching Thunderbird itself finds messages by content, but it will not tell you which file holds them.

Finding it again

Type profiles.ini into Everywhere to land in ~/Library/Thunderbird, or INBOX.msf and check the folder column to see which account each Inbox belongs to. ~/Library/Thunderbird is outside the folders macOS protects, so it is covered without Full Disk Access. It matches file names only, so it cannot find a word inside a message; press ⌘T to open a Terminal in the folder you pick.

Common questions

Where is the Thunderbird profile folder on a Mac?

In ~/Library/Thunderbird/Profiles/, in a folder named like xxxxxxxx.default-release. Thunderbird's Help > Troubleshooting Information page has a Show in Finder button for it.

Where does Thunderbird store emails on a Mac?

Inside the profile: IMAP accounts under ImapMail, and POP accounts and Local Folders under Mail. By default each folder is one extensionless mbox file with a .msf summary beside it.

How do I move my Thunderbird profile to a new Mac?

Quit Thunderbird, then copy the whole ~/Library/Thunderbird folder to the same place on the new Mac, or use Thunderbird's Export and Import tools. Never open the same profile from two running copies of Thunderbird.

What is profiles.ini in Thunderbird?

A file in ~/Library/Thunderbird that lists each profile and its path. Mozilla says to edit its Path and IsRelative lines when you have moved a profile by hand, with Thunderbird closed.