When Firefox syncing is enabled, bookmarks, open tabs, logins, history and add-ons will be available on various other devices which are added to the sync list.
This is handy for ensuring a consistent cross-platform browsing experience. As long as Firefox is installed on different devices with the same account login, this data can be synced.
However, it may happen that a device is now no longer used or doesn’t require this anymore. It can hence be removed from syncing.
To do this :
First, access Firefox preferences by typing in address bar :
Next, go to Firefox Account and click on Manage account.
This will open the Firefox Accounts page from where various account details can be managed. Choose Devices & apps.
A list of all the different devices will be listed with the last sync period and their locations. To remove a device, click Disconnect.
Specify a reason if want to and choose Disconnect.
The device will now longer be synced with Firefox.
All done.