Hello,

Provided you are running the latest version of Firefox on all of your devices and computers, you can sign in with a Firefox account . All you need is an email and password, the sync key is no longer required. Simply click on the menu button (3 bars) and click Sign in to Sync. If you don't already have one, you can create a Firefox account on that page. To add additional devices, log in with the account you just created.

Note: If you don't see Sign in to Sync, you are signed in with your old account and need to follow the steps in Sync your Firefox bookmarks, history, passwords and more.

See:

• How do I set up Sync on my computer?

"in the old firefox synchronized without an email address, using the id" That goes back to the days before Sync was called Sync. Prior to Firefox 4, is was an extension called Weave for Firefox 3.5 and 3.6 versions.

As Shawn mentioned, all that is needed with Firefox 29+ versions of Firefox is the Email Address and the Password.

1. Unlink all your devices. (under the "Device Name" in Options > Sync)
2. Create a new Sync account and wait awhile for you data to be sent to the server.
3. Then one at a time connect each device to that new Sync account, allowing sufficient time for the data to be synchronized.