Want to know what EndNote has to offer? Try our  free  series that guides you through the entire process. Read more here.

Where to store your EndNote library, or not to store it

The EndNote library is a database and can thus be corrupted. Further, the EndNote synchronisation process is sensitive to the location where the library is stored.

If the storage location is a network drive or an external drive, this can cause latency issues when saving and sending information, potentially disrupting the library. Even more disruptive can be ANY process that attempts to copy EndNote Library files while the EndNote library is open.
This includes any backup process that dynamically scans and transfers data. Backup processes like Time Machine, Backblaze, and Carbonite can perform this way. As with most synchronisation services, please avoid iCloud, Dropbox, OneDrive, SuiteSync, Google Drive, Box, etc.

If the EndNote library is stored in a hostile location, Sync is eventually going to collapse as the library becomes more and more damaged by conflicts during EndNote’s save process.
The solution is to save the library in a location that is not hostile (local and not synced by anything).
 

The above does not apply to EndNotes included sync functionality.

Where to store the library 

Alfasoft cannot tell you where to store your library, as the setup of every computer varies. 
All we can do is explain where you should not store your library, and why.

Basically, do not store your library in a location that is not local on your computer or is in any way synced by third parties.

Technical explanation

The technical reason is that EndNote needs to save several files in a specific order. If one of these files is simultaneously synced (locked), then EndNote cannot save to it, and the library may be corrupted. Always make sure your library file is local to the system’s hard drive, and not on a network drive, or in an iCloud, Dropbox, or OneDrive-style synchronised folder.
Read a more detailed technical explanation in this article: Technical reason to use EndNotes sync functionality and nothing else 

Mac

For specific Mac considerations (iCloud) see this article: EndNote, iCloud, Sync and storage location