Syncing makes the references in your EndNote Desktop and EndNote Online libraries exactly the same.

[Video] EndNote Sync: EndNote X7.1 or Later

Video produced and kindly shared by EndNote Training.

Sync Preferences

• It is not necessary to enter e-mail addresses and password each time you synchornize your references between EndNote Desktop and EndNote Online.
• EndNote automatically begins the Sync process every 15 minutes (background processing) by selecting the Sync Automatically check box.

Note: To access Sync Preference, go to Edit, Select Preferences, and then click Sync in the list of preferences.

EndNote X7.1 (or later) can synchronize an unlimited number of references and 5,000 groups between an EndNote Online and your EndNote Desktop library. References can also be synchronized to a second desktop computer and/or an EndNote iPad library. For the first synchronization on any device, there are several important considerations.

• Make a backup copy of your EndNote Desktop library before your first synchronization by selecting Compressed Library from the File menu. This provides a backup in case you have problems. EndNote will prompt you to create a backup, but this command can be used to create a backup of your library at any time. This backup will have an .enlx extension.
• For the first synchronization on any device, ALL references and groups will be copied in both directions. This will result in duplicates if the same references reside on the device and EndNote Online.
• All references and groups will be synchronized, but group sets, smart groups, and combination groups (group from groups) will not be displayed in your online library. Therefore, if two custom groups in an EndNote Desktop library have the same name, but are under different group sets, they will have the same name in EndNote basic, but will have no group set to distinguish them. Consider adding prefixes representing group sets to custom group names to more easily tell them apart in EndNote online before your first synchronization.
• If you synchronize to a second or third computer using EndNote X7.1 or later, all groups and group sets will appear on the second computer.
• Only one EndNote library on a device and one EndNote online account can be synchronized and shared.
• Syncing is not a backup system. If you delete references or attachments from one library, they will be deleted from the other synchronized libraries with the next sync. Technical support will not be able to restore references you have deleted and then synced, so making frequent backups of your desktop library is essential.
• Synchronization will always be of the complete library. There is no selective sync.
• To begin syncing, click the Sync button, then follow the menus to create an EndNote online account or sign in to an existing account. It may take a very long time to sync a large library the first time, so please be patient.