Shared folders use space in each member’s account, unless each person is on the same Dropbox Business team.
Your Dropbox storage quota is calculated by adding up the total amount of data in your Dropbox account. This includes all shared folders you are a member of and all files collected from file requests.
If someone shares a folder with you that is larger than the amount of space you have left, you won’t be able to join the folder. For example, if you have a Dropbox Basic 2 GB account, and you’ve used 1.5 GB of space, you can’t accept a shared folder larger than .5 GB.
If you need to view shared files that are larger than the remaining space in your account, you can:
How do shared links affect my storage space?
Links shared with you don’t take up space in your account, and you can download those files to your computer. If you download a file from a shared link, you can edit your downloaded copy. However, your edits won’t sync with the original file that was shared with you.
Do shared folders affect my storage space if I’m a Dropbox Business team member?
If you’re a member of a Dropbox Business team, the size of a shared folder only counts once against the entire team's shared quota.