One option to back up your EndNote Library is to save a copy. The library recommends this copy to be saved on an external drive to avoid having more than one library at a time on your computer. Note: There are two files to an EndNote library and both will need to be moved and stored together.
From within EndNote:
Click File > Save a Copy.
Video Instructions
An EndNote Compressed Library is currently the recommended method to back up your library. It stores the .enl file and the folder containing the information of your library together as an .enlx file.
This option also allows for backups of certain group/s rather than the entire library.
To create a new backup:
Video Instructions
Syncing your EndNote desktop library with an online account allows you to share your library across multiple computers. It is not recommended that you use this option as a backup.
To set syncing up:
The Sync Status page will have important information including