This is kind of the opposite. With Selective Sync, the file exists on Dropbox.com and 0 or more client devices, and each device can choose whether or not to syn

This is kind of the opposite. With Selective Sync, the file exists on Dropbox.com and 0 or more client devices, and each device can choose whether or not to sync the file. The new ignore feature allows a file to exist on one device without being uploaded or synced to other devices.