Hi This support article should help: https://support.mozilla.org/en-US/kb/how-do-i-choose-what-information-sync-firefox

Note that Sync is about all or nothing, you can't select on each device what to sync. Using Sync means that data from each device is uploaded to the Sync server and merged to all other devices connected to this Sync account. This means that it isn't possible to keep work and home separated when it comes to enabling a specific engine for Sync. It is possible to exclude the theme by settings its control services.sync.prefs pref to false. *about:config => services.sync.prefs.sync.extensions.activeThemeID = false You can exclude the home page and startup page setting from Sync by setting these prefs to false page. *about:config => services.sync.prefs.sync.browser.startup.homepage = false *about:config => services.sync.prefs.sync.browser.startup.page = false ---- *https://support.mozilla.org/en-US/kb/about-config-editor-firefox