What Happens When You Sign Out of iCloud on Mac

The sign-out flow in System Settings asks a rapid series of "keep a copy?" questions that make it feel like your data is about to evaporate. The reassuring truth: signing out removes things from this Mac, not from iCloud. The one real hazard is online-only files you never downloaded.

The one rule to remember

Signing out disconnects the Mac from your account. Everything stored in iCloud — photos, Drive files, notes, contacts — stays on Apple's servers and on your other signed-in devices, untouched. The prompts are only asking: "should this Mac keep its own local copy?" Answer yes generously; local copies cost disk space, not data.

What the keep-a-copy prompts cover

When you sign out (System Settings → your name → scroll down → Sign Out), macOS walks through the data types that have local/cloud versions:

• iCloud Drive files: choose Keep a Copy and the Mac copies your Drive contents into a folder called iCloud Drive (Archive) in your home folder.
• Photos: if your library is set to Optimize Mac Storage, full-resolution originals may live only in iCloud. Keeping a copy triggers downloading originals — which can take hours and serious disk space for a big library.
• Contacts, Calendars, Reminders, Safari data: small; keep copies of all of them.
• Keychain passwords: you can keep passwords on this Mac, but they stop syncing and updating across devices.

Things with no local/cloud ambiguity simply stop working on this Mac: Find My Mac turns off, Messages in iCloud stops updating, Handoff and Continuity features disconnect, and App Store purchases need a fresh sign-in.

The real hazard: online-only files

Files in iCloud Drive (and Desktop & Documents, if synced) can be dataless — visible in Finder but existing only in the cloud, marked with a cloud-and-arrow icon. The archive created at sign-out contains what's on the Mac; files you never downloaded aren't lost, but they also aren't in the archive — they remain in iCloud only. If your goal is a fully self-contained Mac, download everything first:

1. Open iCloud Drive in Finder, select all (⌘A), right-click and choose Download Now.
2. In System Settings → your name → iCloud → iCloud Drive, turn off Optimize Mac Storage so macOS stops evicting files to save space, and wait for downloads to finish.
3. Check the Photos question separately — if Photos shows Optimize Mac Storage, switch to Download Originals to this Mac in Photos → Settings → iCloud and let it complete.

Signing back in later

Nothing about signing out is final. Sign back in and the Mac reconnects to everything on the server; sync resumes as if you'd set up a new machine. The one messy leftover is the iCloud Drive (Archive) folder — after re-signing in you'll have the archive and the live iCloud Drive, so reconcile duplicates manually before deleting the archive. If you're signing out to hand the Mac to someone else, don't stop here: erase it properly with Erase All Content and Settings so Activation Lock and your data go with you.

Side effects people forget

A few dominoes fall that the prompts don't spell out. If your email is @icloud.com, Mail on this Mac stops sending and receiving until you sign back in (the mailbox itself lives on the server and is fine). Any purchases mid-download from the App Store pause. Apple Pay cards tied to the Mac are removed. And because Find My Mac turns off at sign-out — Apple requires your password precisely so a thief can't do this silently — the Mac drops out of your Find My device list entirely. If the machine is a laptop that leaves the house, that's a real security downgrade to weigh before signing out casually.