iCloud & iCloud Photos · Online-only files and Optimize Mac Storage
How can I tell an iCloud Drive file has finished uploading?
Short answer: In Finder, uploading files show a progress or cloud-with-arrow icon and iCloud Drive's sidebar entry shows a progress circle; when they disappear, the upload is done. You can also add an iCloud Status column in List view.
In Finder, files still uploading show a small progress or cloud-with-arrow icon beside their names, and iCloud Drive in the sidebar shows a progress circle while it works. When those disappear, the file is in iCloud. In List view you can also add the iCloud Status column (View → Show View Options).
Wait for uploads to finish before making files online-only or erasing a Mac. Storage Studio does this for you — it skips files iCloud hasn't safely stored yet. See what the cloud icons mean.