Creating multiple sync profiles in Firefox

Solution 1:

Firefox associates one profile with one Mozilla user account. You can use the same collection of profiles on different devices, say "Personal" and "Work", and sync each profile on all devices with the same associated user account, so all devices would sync the "Work" profile with the "Work" account, and all would sync the "Personal" profile with the "Personal" account.

Note that for a given profile/account, the devices do not need to sync the same choice of details. For example, you could set "Work" on one device to sync only bookmarks with the other "Work" profiles, while other devices sync bookmarks, extensions, history, etc. There is a selection of kinds of details available to sync. The account syncs the collection of details, but only devices set to sync a specific kind of detail will feed, or update from, that detail for the account.

The user account is tied to an email address, which serves two purposes. It is a unique key that the profile on each device is associated with. The profiles on two devices don't need to have the same names, they just need to be associated with the same user account via the email address. So "Lio-personal" could be the profile name on one device, and "Me" could be the profile name on another device, and they will be synced with each other if both are linked to the same email address.

Mozilla also uses the email address for security. If you install Firefox on a new device and then set up syncing with an existing account, you will get a message at the associated email address advising you that "someone tried to sync with your account; ignore this message if it was you."

I don't know how far Mozilla goes to ensure that email address are valid and remain valid for security purposes. I suspect you could not create a user account with a fictitious email address that only provides a unique key, and I don't know whether sync would continue to work for long if the email address becomes invalid. That's a tangent you can investigate if it might apply.

So each user account needs a different email address. However, some email services let you create aliases for the same account. You could use such aliases for the purpose of having separate Mozilla accounts for the different profiles.