Firefox Sync works by storing your data on Mozilla servers and syncing it with your computers and devices. When you set up Sync, you enter a username and password order to prevent others from accessing your account. In addition, we encrypt your data with a Sync Key in order to keep your it safe on the server. This article explains what to do if you forget or loose any of this important information and are unable to access your Sync account.

I've lost my Sync Key

If you don't have a copy of your Sync Key saved anywhere, another computer or mobile device that's synced (see Sync your Firefox bookmarks, history, passwords and more), you can generate a new one.

1. In the Menu bar at the top of the screen, click Firefox and select Settings (select Preferences on older macOS versions).Click the menu button and select Settings.
2. Click on the Sync panel.
3. Click Set up Firefox Sync and a new window will open.
4. Under I already have a Firefox Sync account, click Connect.
5. Click I don't have the device with me.
6. Enter your account email address and password.
7. Click I have lost my other device and a new Sync Key will be made for you.
   Tip: It's a good idea to print or save your Sync Key so that you can access your information even when you are away from this computer.
8. Then click Change Sync Key. You will see the Setup Complete screen.
9. Click FinishDone to close the setup window.

I’ve forgotten my Sync password — how do I reset it?

To get a new password follow these steps.

1. Go to https://account.services.mozilla.com.
2. Click Forget your password?.
3. Enter your username (this is the email address you used when you created your Sync account) and fill in the captcha to prove that you're a real person.
4. Click Email Reset Key. You will receive and email with a link.
5. Open the email, click the link and new page will be open.
6. Type your new password twice.
7. Click Change My Password to save.

Now you're ready to go. Remember to update your password on all your synced devices by clicking Sync Now and Preferences... in the bottom error bar that will displayed.

I’ve forgotten or no longer have access to my Sync email address

Unfortunately there's no way to change or recover the email address associated with a Sync account. You would need to create a new account following the steps described in How do I set up Sync on my computer?.

I've forgotten my master Firefox password

For security reasons, your master Firefox password is not synced. If you've forgotten your master password and want to stay synced, you'll need to reset your master password and re-add your computer to Firefox Sync.

1. Reset your master password by following instructions in Reset your Primary Password if you've forgotten it.
2. Click the Firefox menu and select Exit.Click the Firefox menu at the top of the screen and select Quit Firefox.Click the Firefox menu and select Quit.
3. Start Firefox
4. Re-add your computer to Firefox Sync.