iCloud & iCloud Photos · Online-only files and Optimize Mac Storage
What are the hidden .icloud files on my Mac?
Short answer: On older macOS, an online-only iCloud file is shown on disk as a hidden placeholder ending in .icloud. It stands in for the real file until downloaded. Don't delete it — that can delete the file from iCloud.
On older versions of macOS, an online-only iCloud file was represented on disk by a small hidden placeholder whose name ended in .icloud. It stands in for the real file until you download it. Newer macOS versions show online-only files as normal items with a cloud icon instead.
Don't delete these placeholders to "clean up" — removing one can delete the real file from iCloud. To download the file, open it from iCloud Drive in Finder; to free space, use online-only features rather than deleting anything.