Login in where or login to what?

If it is a web site, most will have a '''Forgot Your Password''' link on the sign in page.

Note that Sync isn't meant to be used as a backup in case your question is about Sync. It is always best to backup your Firefox personal data locally yourself. *http://kb.mozillazine.org/Profile_backup *https://support.mozilla.org/kb/Backing+up+your+information

These add-ons can be a great help by backing up and restoring Firefox '''[https://addons.mozilla.org/en-US/firefox/addon/febe/?src=collection&collection_id=33bf10fa-666d-45a2-9bc9-491ce21671c6 FEBE (Firefox Environment Backup Extension)]''' {web link} FEBE allows you to quickly and easily backup your Firefox extensions, history, passwords, and more. In fact, it goes beyond just backing up -- It will actually rebuild your saved files individually into installable .xpi files. It will also make backup of files that you choose. '''[https://addons.mozilla.org/en-US/firefox/addon/opie/?src=collection&collection_id=33bf10fa-666d-45a2-9bc9-491ce21671c6 OPIE]''' {web link} Import/Export extension preferences