'''Firefox Sync''' is a browser synchronizer "system" which allows users to keep their Firefox web browser configured in the same way on different computers, devices, and operating systems. For instance, if a user adds a bookmark while being at home, the bookmark will be available the day after at office; along with many other types of personal data. See this: <br />https://support.mozilla.org/en-US/kb/firefox-sync-take-your-bookmarks-and-tabs-with-you '''Can I use my Yahoo email account? ''' <br /> Yes, you can use your Yahoo email account username for your username / email address when you setup Sync.