EndNote is available for Windows™ & Macintosh™ and can also be used online. Please check Compatibility, system & word processor requirements

EndNote X8.2
All recent versions of EndNote have been backwardly compatible and you should not experience any disadvantage using X9 and updating to 20 at a later date. 

If you are using a copy of EndNote installed on your personal computer, you may see a pop-up window promoting EndNote 20 when you launch the application. You can select the Ignore This option to prevent the pop-up from reappearing.

Cloud-based Storage
EndNote is not compatible with cloud-based storage services including:

• OneDrive (Microsoft’s cloud storage service)
• Dropbox
• OneNote (Microsoft™)
• iCloud (Apple™)
• Google Drive.

Your working EndNote library and any Word documents containing EndNote field codes should be saved to the hard disk of your computer. 

Using cloud-based storage to store your EndNote library will result in poor performance and a corrupt library, rendering the library unusable.

Using EndNote with any Word documents located in cloud-based storage will result in a corrupted Word document that will be unusable.