iCloud Drive's promise is simple; its disk behavior is not. Even with Optimize Mac Storage enabled, many users find 20-80 GB of iCloud documents fully materialized on disk. macOS is supposed to keep only placeholders — but eviction is a suggestion, not a rule.

See what is actually local

du -sh ~/Library/Mobile\ Documents/com~apple~CloudDocs 2>/dev/null
# per-folder:
du -sh ~/Library/Mobile\ Documents/com~apple~CloudDocs/* 2>/dev/null | sort -h

(Finder's iCloud Drive is this folder; file providers for third-party clouds live in siblings under Mobile Documents.)

Force-evict a folder

The supported way: right-click a folder in Finder → Remove Download. It stays in iCloud, becomes a placeholder locally, and re-downloads on open. For stubborn folders that never evict:

• Confirm Optimize Mac Storage is on (System Settings → Apple ID → iCloud → Drive)
• Check free space: macOS evicts aggressively only when the disk runs low — on a half-empty disk it happily keeps everything
• Last resort: toggle iCloud Drive off/on for that Mac (re-syncs; keep a backup of anything critical first)

The honest alternative

If a folder is archival (old projects, media masters), it does not belong in a sync folder at all. Move it to cold storage and delete from iCloud — sync services are for working sets, not archives. Pair this with our System Data walkthrough to see how much of your grey bar was iCloud all along.

Related

iCloud evictions, Time Machine snapshots (guide), and simulator data are the three "invisible by design" eaters. For everything visible at a glance: DaisyDisk vs free alternatives, or the ten-second waste estimator.