Dropbox allows users to choose which files they want to sync across their devices, rather than syncing everything by default. To do this, users can access the Preferences window and select the Selective Sync option, allowing them to uncheck specific files or folders that should not be synced. This feature is tied to individual computers, meaning each device has its own set of synced files, but it also allows for flexibility in managing which files sync across multiple devices. By using selective syncing, users can conserve bandwidth and hard drive space, while still being able to access their files through the web or mobile version of Dropbox.