Why does the icon have a check mark?
MacBook Pro, macOS Mojave (10.14)
Dropbox confirms uploads were a success. Whats new?
A green circle with a check mark means a file or folder has finished syncing the latest changes. These could be changes you made, or changes made by someone you shared the file or folder.
The sync icons on files in the desktop app, and what to do if they’re missing – Dropbox Help
See? Just as I thought. 😎
As a guess I would say it's caused by one of the third party cloud apps such as Dropbox, Google Backup & Sync, etc. letting you know they were successfully uploaded.
Why does the icon have a check mark?