Thunderbird profile location and key files

Thunderbird stores mail, account settings, address books, filters, calendars and other local data inside a profile folder. This article shows where that profile is normally stored on Windows, macOS and Linux, and explains the most common files and folders found inside it.

What a Thunderbird profile is

A Thunderbird profile contains user-specific data such as:

• email accounts and account settings
• downloaded mail and local folders
• message filters
• address books
• calendars and tasks
• saved passwords
• signatures, preferences and customisations
• add-ons and some cache data

A profile is separate from the Thunderbird program files. Uninstalling Thunderbird does not usually remove the profile.

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Default Thunderbird profile locations

Thunderbird normally stores one or more profiles in a Profiles directory, with each profile in a folder named something like xxxxxxxx.default-release.

Windows

Main profile location

C:\Users\<username>\AppData\Roaming\Thunderbird\Profiles\

Thunderbird configuration files

C:\Users\<username>\AppData\Roaming\Thunderbird\

Cache location

C:\Users\<username>\AppData\Local\Thunderbird\Profiles\

Quick access via Run

%APPDATA%\Thunderbird\Profiles\

or

%APPDATA%\Thunderbird\

macOS

Main profile location

/Users/<username>/Library/Thunderbird/Profiles/

Thunderbird configuration files

/Users/<username>/Library/Thunderbird/

Cache location

/Users/<username>/Library/Caches/Thunderbird/Profiles/

Linux

Main profile location

~/.thunderbird/

Profiles are normally inside:

~/.thunderbird/<profile-name>/

Typical example:

~/.thunderbird/abcdefgh.default-release/

Cache location

Depending on distribution and Thunderbird version, cache may appear under:

~/.cache/thunderbird/

or inside the profile.

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How to identify the active profile

If more than one profile exists, the active one is usually listed in the profiles.ini file.

Windows

%APPDATA%\Thunderbird\profiles.ini

macOS

/Users/<username>/Library/Thunderbird/profiles.ini

Linux

~/.thunderbird/profiles.ini

This file maps profile names to profile folder paths and indicates which one is the default.

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Common profile folder layout

Inside a Thunderbird profile, common folders and files include:

Mail/
ImapMail/
Local Folders/
Calendar/
storage/
extensions/
prefs.js
abook.sqlite
history.sqlite
key4.db
logins.json
msgFilterRules.dat
pkcs11.txt
cert9.db
permissions.sqlite
folderTree.json
panacea.dat
xulstore.json
session.json

Not every profile will contain every item. Some files appear only after specific features are used.

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Key Thunderbird files and what they do

Core configuration files

prefs.js

Main settings file for the profile.

Stores:

• account configuration
• server names and ports
• identities and signatures
• UI preferences
• add-on settings
• many internal Thunderbird options

Important notes:

• this is one of the most important files in the profile
• corruption can cause account settings to disappear or behave unexpectedly
• it should only be edited with Thunderbird closed

profiles.ini

Stored one level above the profile, not usually inside it.

Purpose:

• lists available profiles
• identifies the default profile
• tells Thunderbird where each profile is stored

installs.ini

Used by newer Thunderbird versions to associate an installation with a profile.

Purpose:

• helps Thunderbird decide which profile to open for a particular installed copy

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Mail storage files and folders

Mail/

Stores mail for POP accounts and Local Folders.

Typical subfolders include server names and local archive folders.

ImapMail/

Stores local copies and synchronisation data for IMAP accounts.

Important notes:

• IMAP mail remains on the server unless folders are explicitly configured otherwise
• local cache and offline copies are kept here

Local Folders/

Usually found under:

Mail/Local Folders/

Purpose:

• stores local-only folders
• commonly used for archives, imported mail and manually filed messages

Mbox mailbox files

Thunderbird commonly stores mail folders as mbox files with no file extension.

Examples:

Inbox
Sent
Drafts
Archives
Projects

Purpose:

• each file contains all messages for that folder

Important notes:

• these can become very large
• if they are damaged, mail in that folder may become inaccessible

.msf files

Examples:

Inbox.msf
Sent.msf

Purpose:

• message summary index files
• used by Thunderbird to display folder contents quickly

Important notes:

• these do not contain the actual email messages
• if damaged, they can usually be deleted and rebuilt by Thunderbird
• deleting an .msf file does not normally delete the email itself

.sbd folders

Example:

Projects.sbd/

Purpose:

• stores subfolders for a mail folder
• if a Thunderbird folder contains child folders, they are often held inside a matching .sbd directory

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Message filtering files

msgFilterRules.dat

Stores message filters for an account or local folder set.

Purpose:

• defines rules such as moving, tagging, forwarding or deleting messages
• used for Thunderbird's built-in filtering system

Important notes:

• there may be more than one msgFilterRules.dat
• it is usually stored inside each account’s mail directory, for example in folders under:

Mail/

or

ImapMail/

Typical locations might look like:

Mail/pop.example.com/msgFilterRules.dat
ImapMail/imap.example.com/msgFilterRules.dat
Mail/Local Folders/msgFilterRules.dat

If filters are missing, this is one of the first files to check.

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Address book files

Older Thunderbird versions used .mab files, while modern versions use SQLite databases.

abook.sqlite

Personal address book.

Purpose:

• stores user contacts in the main local address book

history.sqlite

Collected addresses.

Purpose:

• stores automatically collected email addresses, depending on configuration

Older files: abook.mab and history.mab

Used by older Thunderbird releases.

Purpose:

• legacy address book format
• may still exist in older migrated profiles

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Password and certificate files

logins.json

Stores saved website and mail passwords in encrypted form.

Purpose:

• contains saved login entries for accounts and services

Important notes:

• this file works together with key4.db
• both are normally required to preserve saved passwords

key4.db

Encryption key database.

Purpose:

• stores keys used to protect saved passwords and other secrets

Important notes:

• if logins.json is copied without key4.db, saved passwords may not be usable

cert9.db

Certificate database.

Purpose:

• stores imported certificates and certificate trust information
• relevant for S/MIME, client certificates and some security configurations

pkcs11.txt

Security device configuration.

Purpose:

• stores PKCS#11 module configuration
• used when hardware tokens or smartcards are configured

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Calendar and task data

calendar-data/

Local calendar support data.

Purpose:

• stores some calendar cache and local calendar information

storage.sqlite

Calendar and task database in many Thunderbird configurations.

Purpose:

• stores local calendars, tasks and related data

Important notes:

• if calendars are connected to remote services, Thunderbird may also store cache and metadata for them locally

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Search, indexing and database files

global-messages-db.sqlite

Global search and indexing database.

Purpose:

• provides Thunderbird’s global message search
• supports quick searching across accounts

Important notes:

• this file can become large
• if search is broken, Thunderbird can usually rebuild it

panacea.dat

Folder cache file.

Purpose:

• stores information about folders and message store structure
• helps Thunderbird load folder data more quickly

folderTree.json

Folder pane state.

Purpose:

• stores how folders are shown in the folder tree
• includes UI state such as expanded and collapsed folders

xulstore.json

Interface customisation state.

Purpose:

• stores toolbar layouts, window positions and some UI settings

session.json or related session files

Session state.

Purpose:

• stores details about open windows, tabs or restart state

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Permissions and content storage

permissions.sqlite

Site and content permissions database.

Purpose:

• stores permissions for remote content and certain security prompts

storage/

Web-style local storage used by Thunderbird components and add-ons.

Purpose:

• stores internal application and extension data

extensions/

Installed add-ons and related extension data.

Purpose:

• stores extension packages and supporting files

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File importance for backup and migration

For most profile backups or transfers, the most important items are:

• the entire profile folder
• profiles.ini if multiple profiles exist
• mail folders under Mail/ and ImapMail/
• prefs.js
• msgFilterRules.dat
• abook.sqlite
• history.sqlite
• logins.json
• key4.db
• cert9.db
• calendar data such as storage.sqlite

Best practice:

• close Thunderbird before copying profile files
• copy the whole profile rather than selected files where possible
• keep a backup before editing or restoring individual files

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Notes on older and newer Thunderbird versions

Thunderbird has changed some file formats over time. Common examples:

• address books changed from .mab to .sqlite
• some UI and cache files differ by version
• profile folder names may include labels such as:

.default
.default-release
.default-esr

These differences are normal.

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Quick reference

Windows

C:\Users\<username>\AppData\Roaming\Thunderbird\Profiles\
C:\Users\<username>\AppData\Roaming\Thunderbird\profiles.ini

macOS

/Users/<username>/Library/Thunderbird/Profiles/
/Users/<username>/Library/Thunderbird/profiles.ini

Linux

~/.thunderbird/
~/.thunderbird/profiles.ini

Key files

• prefs.js — account and application settings
• msgFilterRules.dat — message filter rules
• abook.sqlite — personal address book
• history.sqlite — collected addresses
• logins.json — saved passwords
• key4.db — encryption keys for saved passwords
• cert9.db — certificates
• global-messages-db.sqlite — search index
• storage.sqlite — calendar/task data
• mailbox files such as Inbox, Sent — actual mail storage
• .msf files — folder indexes only

Related articles

• Backing up a Thunderbird profile
• Migrating Thunderbird to a new computer
• Repairing missing folders or rebuilding Thunderbird indexes
• Exporting or restoring Thunderbird address books