The short answer
No. Your data. Shrink it from its app; don’t delete the folder.
What is it?
~/Library/Mobile Documents is where iCloud Drive keeps its files on your Mac, including Desktop and Documents if you sync them, and app folders such as Pages or Numbers. Only files currently downloaded take local space.
Files kept on this Mac that are also in iCloud. Free the local copy; the file stays in iCloud and downloads again when opened.
What happens if you delete it?
Deleting files here deletes them from iCloud and all your devices (they stay in Recently Deleted on iCloud.com for 30 days). Removing just the download keeps the file in iCloud, and it downloads again when you open it.
How to remove it properly
Never delete this folder. In Finder, right-click files or folders in iCloud Drive and choose Remove Download. To let macOS do this automatically, open System Settings, click your name, then iCloud › Drive and turn on Optimize Mac Storage.
From the app itself: Finder: right-click files or folders > Remove Download, or turn on Optimize Mac Storage in iCloud settings.
Before you delete it
Only files that have finished uploading can be freed. Files that exist only in iCloud are not included in Time Machine backups of this Mac.
How MoreRoom helps
MoreRoom recognises this as your data and never suggests deleting it. It shows how much space it takes, so you can shrink it from its own app.
Frequently asked questions
Can I delete Mobile Documents (iCloud Drive) to save space?
No. Your data. Shrink it from its app; don’t delete the folder. Deleting files here deletes them from iCloud and all your devices (they stay in Recently Deleted on iCloud.com for 30 days). Removing just the download keeps the file in iCloud, and it downloads again when you open it.
Will iCloud Drive (local copies) come back after I delete it?
No. Deleting files here deletes them from iCloud and all your devices (they stay in Recently Deleted on iCloud.com for 30 days). Removing just the download keeps the file in iCloud, and it downloads again when you open it.
How do I remove iCloud Drive (local copies) properly?
Never delete this folder. In Finder, right-click files or folders in iCloud Drive and choose Remove Download. To let macOS do this automatically, open System Settings, click your name, then iCloud › Drive and turn on Optimize Mac Storage.