If you see the error "Your startup disk is almost full.” on Mac or “You are running out of disk space on [Drive name].” on Windows, then your computer is low on hard drive space.
If you see the error “Your Dropbox is full.” then your Dropbox account is out of storage space.
To check your available hard drive space on a Mac computer:
To check your available hard drive space on a Windows computer:
Open Computer, where you should see how much free space you have left. If it does not, right-click on your hard drive and select Properties from the menu.
For Dropbox to sync completely, you need at least the same amount of hard drive space free as the amount of data in your Dropbox account. If you're trying to move files into your Dropbox folder from an external hard drive, you'll need to make sure you have enough space on your Dropbox account as well as your computer's hard drive to do so.
Dropbox will sync files to the Dropbox folder on your hard drive until it reaches capacity. Once your hard drive is full, you'll have to make room on your hard drive to sync more files. Even if your hard drive is full, your files are always available for access from the dropbox.com.
If you find yourself with a hard drive smaller than your Dropbox account, or you'd like to free up space on your computer, you can choose which files to sync to your computer via selective sync. Your Selective Sync settings can be found in the Dropbox desktop app settings.