How to Migrate Thunderbird to a New Computer: Profiles and Mail
To migrate Thunderbird to a new computer, close Thunderbird on both machines, install Thunderbird on the destination computer, then copy the entire profile folder from the old machine over the default profile that installation just created. That profile folder holds your messages, account settings, contacts, calendars, preferences, installed extensions, and other data, so moving it is the broadest way to bring your email setup along in one pass. Two other paths work for smaller jobs: Thunderbird’s built-in Export tool for profiles up to 2 GB, or a third-party migration tool. Check extensions after the new setup is running, since they may need attention after launch.
What to Do Before You Migrate Thunderbird
A few minutes of preparation before moving to a new computer prevents most migration headaches. Work through this checklist on both computers before you touch a single file.
- Close Thunderbird completely on the old computer and, if it is already installed, on the new one too. A running profile can lock files mid-copy.
- Install the latest Thunderbird release on the destination computer, or match the version already running on the source machine, so the profile opens without a version conflict.
- Back up your data first, even though you are about to copy it elsewhere. A second copy on a separate drive protects you if the transfer goes wrong.
- Turn on the display of hidden files and folders in your file explorer, since the AppData folder on Windows and the Library folder on a Mac are hidden by default.
- Confirm the destination computer has enough free disk space for the profile folder, particularly if years of messages and attachments have built up.
- If the move crosses operating systems, expect to deal with different path formats and file permission rules once the files land on the new machine.
Skipping any one of these steps rarely stops the migration outright, but it tends to show up later as a missing folder, a locked file, or a profile that Thunderbird refuses to open.
How to Migrate Thunderbird to a New Computer
Every account, message, and setting rides along, because the profile folder holds the entirety of your Thunderbird data outside the program files themselves.
Follow these steps in order.
- Install Thunderbird on the destination computer. Run it once without setting up an account, then exit. This creates a default profile folder that you will overwrite.
- Open the profile folder on the source computer. Go to the menu icon, then Help, then Troubleshooting Information, then Profile Folder, then Open Folder. Thunderbird opens the exact folder in your file manager, which is safer than typing the path from memory.
- Copy the entire profile folder. Select every file and subfolder inside it and copy the contents to a USB drive or other external storage.
- Move the storage device to the new computer. Plug it in once Thunderbird has been installed and closed.
- Locate the destination profile folder. Use the same Troubleshooting Information menu on the new computer to find where the default profile lives.
- Replace the destination profile contents. Delete or overwrite the default profile’s files with the backed-up ones. If the folder names do not match, open the Profile Manager, create a new profile in the desired location, and paste the backed-up contents into it, overwriting anything already there.
- Launch Thunderbird and check your data. Confirm that accounts, folders, messages, and contacts all appear before you disconnect the storage device.
Remove read-only file attributes from the copied files if you notice messages failing to load after the move. Files copied from some external drives or optical media retain a read-only flag on Windows, which can block Thunderbird from writing to them.
Where Is the Thunderbird Profile Folder Located
The Thunderbird profile folder sits in a different place on each operating system, and the safest way to find it is through Thunderbird’s own menu rather than typing a path from memory.
Windows
Windows keeps the profile folder at C:\Users\[YourName]\AppData\Roaming\Thunderbird\Profiles\.
macOS
macOS stores the profile folder at /Users/[Username]/Library/Thunderbird/Profiles/. Another listed macOS path is /Users/[Username]/Library/Application Support/Thunderbird/Profiles; use Thunderbird’s troubleshooting information to find the active profile.
Linux
Linux systems keep it at /home/[Username]/.thunderbird/, sometimes written as ~/.thunderbird/. A file manager set to show hidden folders makes it easy to browse there directly instead of relying on Thunderbird’s own menu.
Windows Thunderbird Profile Paths at a Glance
On Windows, the main Thunderbird data folder is %APPDATA%\Thunderbird. Individual profiles sit inside its Profiles subfolder, under a folder name assigned to that profile.
| Location | Windows path | What it identifies |
|---|---|---|
| Thunderbird root | %APPDATA%\Thunderbird | The master Thunderbird data folder used for Mozilla’s Windows manual-transfer method. |
| Profiles subfolder | C:\Users\<username>\AppData\Roaming\Thunderbird\Profiles\ | The folder containing individual Thunderbird profile directories. |
| Example individual profile | C:\Users\LeoN\AppData\Roaming\Thunderbird\Profiles\8h1k0c0z.default | One profile directory; replace LeoN with the Windows login name. |
Open the root location directly by pressing Windows + R, entering %APPDATA%\Thunderbird, and opening the result. Profile folders can have names such as 8h1k0c0z.default or abcd1234.default-release.
For a standard full Windows migration, copy the parent Thunderbird folder rather than only one profile folder. Mozilla’s method replaces the destination Thunderbird folder and carries messages, passwords, preferences, and changes; an individual-profile approach suits installations with customised profile locations identified in profiles.ini.
How to Use Thunderbird’s Built-In Export Tool
Thunderbird’s Export tool packages an entire profile into a single ZIP file, and it works for profiles under 2 gigabytes. It is the fastest option for a typical mailbox that has not accumulated years of large attachments.
On the source computer, open the menu icon, then Tools, then Export, and save the resulting ZIP file somewhere you can reach from the new computer, then use the Import function on the destination computer to load it back in.
Export and Import trade a little completeness for convenience. Some metadata can be lost compared with a direct profile copy, so treat this method as the quick option for straightforward setups rather than the choice for a profile with heavy customization.
Manual Copy vs Export Tool vs Third-Party Software
Direct profile copying handles profiles over 2 GB and moves mail, settings, contacts, and other profile data together. The Export tool suits profiles up to 2 GB, while third-party tools are another option described by their vendors. Beyond that, the table below lines up the three approaches.
| Aspect | Manual Profile Copy | Built-in Export Tool | Third-Party Software |
|---|---|---|---|
| Best for | Profiles over 2 GB; complete data transfer | Profiles up to 2 GB | Users considering commercial automation |
| Data preserved | Mail, settings, contacts, and other profile data | Profile backup | Profile data selected for restore or export |
| Time required | Copy the complete profile and replace destination contents | Generates a ZIP file | Select a Thunderbird profile and restore or export its data |
| Risk level | Preserve the original backup and verify the migration | Verify the imported profile | Check vendor claims carefully |
| Add-on transfer | Installed extensions are part of a complete profile; check them after launch | Check extensions after import | Check extensions after migration |
| 2 GB+ support | Yes | No | Depends on the tool |
| Cross-platform support | Paths, permissions, authentication, and extension compatibility may need adjustment | Use Import on the destination installation | Depends on the tool |
Options such as the BitRecover Thunderbird Restore Tool and the DRS Thunderbird Backup Tool fall into the third-party category. Their pages describe selecting a Thunderbird profile and restoring or exporting its data, but manual copying and Thunderbird’s built-in methods remain available alternatives.
Since 2022, my refurbished Lenovo ThinkPad T14 Gen 2 in north Columbus, Ohio has reminded me that a neat transfer plan can become less neat when the files refuse to fit its assumptions. In Manual Copy vs Export Tool vs Third-Party Software, I would check the profile against the export limit before calling ZIP the tidy option; my refurbished laptop was already a compromise, not a religion.
What Transfers to Your New Computer and What Does Not
Migrating the complete profile folder carries over mail, settings, and other Thunderbird data. Checking the migrated setup after launch helps catch anything that needs attention.
What Transfers
Downloaded messages and Local Folders move over, along with POP account mail and IMAP configuration. Other profile data also transfers. Search indexing should also be allowed to complete after the move.
What Does Not Transfer
A complete profile includes installed extensions, so check that they work after the move rather than assuming every extension will work unchanged. Saved passwords may be included in the profile, but they are not guaranteed to work on another computer. Online accounts may require re-authentication after migration.
Common Migration Problems and How to Fix Them
Most Thunderbird migration failures trace back to a handful of known causes, and each has a straightforward fix.
Profile Stored on a Synced Cloud Folder
Never run a live Thunderbird profile from OneDrive, Dropbox, Google Drive, or iCloud Drive, and never share one profile between two computers at the same time. Continuous syncing while Thunderbird writes to its database causes corruption. Copy the profile to a local folder outside any synced directory, then work from there.
Version Mismatch Between Computers
A profile created by a newer Thunderbird release should not be opened with an older release. Use the latest or an identical version of Thunderbird, and if the two machines are on very different versions, update the older one first.
Files Marked Read-Only After Copying
Copies made from a USB drive, CD, or DVD sometimes keep a read-only attribute once pasted onto the new computer. Right-click the copied folder, open its properties, and clear the read-only checkbox before launching Thunderbird.
Profile Loading Failures or Missing Attachments
Interrupted copies, incomplete transfers, and manual mistakes can leave a profile that loads with missing folders or broken attachments. Address book entries can also fail to import cleanly when the transfer was rushed or the storage device was removed too early. Compare the copied folder’s size against the original before deleting any source data, and keep the original profile intact until you have confirmed everything opens correctly on the new machine.
Restoring to a Custom Location
If you restore a profile to a custom folder rather than the default path, Thunderbird will use the existing data automatically as long as it finds a prefs.js file in that same directory. Point Profile Manager at the folder rather than trying to rename files to match the default naming pattern.
Migrating Thunderbird Between Windows, macOS, and Linux
Cross-platform Thunderbird migration works the same way as a same-platform move: copy the entire profile folder to the equivalent location on the new operating system. The profile folder’s internal structure differs only slightly between Windows, macOS, and Linux.
Plan for a few platform-specific snags. Path formats differ, since Windows uses backslashes and drive letters while macOS and Linux use forward slashes. File permissions can also change during the copy, particularly when moving from Windows to Linux, so check that Thunderbird has read and write access to the new profile folder before launching it. Authentication can behave differently across operating systems too, especially for accounts that rely on OS-level credential storage, so be ready to sign back in to those accounts on the new machine.
Frequently Asked Questions
Do I Need to Set up My Email Accounts Again After Migrating Thunderbird?
No, not if you copied the entire profile folder correctly. Account settings, server details, and folder structure are stored inside the profile, so they appear automatically once Thunderbird opens the transferred profile on the new computer.
Will My Saved Thunderbird Passwords Work on the New Computer?
They might not. Passwords stored in key4.db or logins.json usually copy over with the rest of the profile, but OAuth-based accounts, two-factor authentication, and operating-system-specific credential handling can force a fresh sign-in regardless of what was copied.
Can I Migrate a Thunderbird Profile Larger than 2 Gigabytes?
Yes, but the built-in Export tool will not handle it because that tool has a documented 2 gigabyte ZIP limit. Use a direct profile copy or a third-party migration tool instead, since both handle profiles of any size.
Is It Safe to Keep My Thunderbird Profile in a Synced Cloud Folder?
No. Running a live profile from OneDrive, Dropbox, Google Drive, or iCloud Drive risks database corruption because the sync process and Thunderbird can write to the same files at the same time. Keep the working profile on local storage and use cloud storage only for an inactive backup copy.
What Thunderbird Version Should I Install Before Migrating?
Install the latest version, or at least a version equal to or newer than the one that created the original profile. Opening a newer profile with an older Thunderbird release can cause errors, so update the destination computer first if its copy is behind.
A direct profile copy remains the surest route for most people, since it carries every account, message, and setting without the size limits of the Export tool. Whichever method you pick, keep the original profile untouched until the new computer proves it opens cleanly.
References
- How Do I Move Thunderbird to a New Computer?, Ask Leo
- Move Thunderbird Profile to New Computer | Mac & Win (2026), BitRecover
- How to Backup and Restore Thunderbird Emails, Profiles, and Settings, iTechGuides
- Move Thunderbird Profile to New Computer / PC – Reliable Methods, Systoolsgroup
- Top Tips to Move Thunderbird to a New Computer, Data Recovery Solutions
Sources read in September 2026.