Free the space without deleting anything
- iCloud Drive: open System Settings → your name → iCloud → Drive and turn on Optimize Mac Storage. macOS removes local copies of files you haven't used recently.
- One folder right now: in Finder, right-click a folder in iCloud Drive and choose Remove Download. The file stays in iCloud and on your other devices.
- Photos: open Photos → Settings → iCloud and choose Optimize Mac Storage. Full-size originals stay in iCloud.
Never delete files from the iCloud Drive folder to save space. Deleting there deletes them from iCloud and every device. Use Remove Download instead.