By default, the Dropbox app synchronizes all content to your computer. If you run low on disk space, consider using selective sync to exclude larger folders from synchronizing locally. This will not impact the files stored on Dropbox; all files and folders will remain accessible through Dropbox on the web. It will reduce the amount of space your Dropbox data consumes on your computer.
With Smart Sync, you can see and seamlessly access all the content you have in your Dropbox, right from your desktop, without worrying about local hard drive space. Files and folders take up practically no space on the local device until they’re needed, and they can be accessed with a simple click.