To export (back up) the contacts in a FritzBox address book, proceed as follows:

• Open the FritzBox app in your browser at "fritz.box" and log in with your password.
   
• Click on "Telephony" in the left-hand table of contents and then on "Phone Book".
   
• Click on the tab with the name of the phone book you want to export.
   
• Click on the "Backup" button at the end of the contact list.
   
• Click on "Save as" and select a folder in which to save the XML file. You can also change the default file name if you wish. In any case, make a note of the location of the file for future use.