Why iCloud Drive Stops Syncing on Mac
iCloud Drive sync failures are one of the most common macOS issues in 2026. A CloudKit bug introduced in iOS/macOS 26.4 (patched in 26.4.1) caused widespread sync stalls — but even after updating, many Macs continue to show files stuck in a "Waiting" or "Uploading" state. This guide covers every fix, from the simple (sign out and back in) to the advanced (resetting iCloud daemons).
Step 1: Check Your iCloud Status and Storage
First confirm iCloud isn't down server-side:
- Visit apple.com/support/systemstatus — iCloud Drive must show a green dot.
- Check your iCloud storage: System Settings → [Your Name] → iCloud → Manage Storage. If storage is full, nothing will sync until you free space.
Step 2: Update to the Latest macOS
The CloudKit syncing bug in macOS 26.4 was fixed in 26.4.1. If you haven't updated:
System Settings → General → Software Update
Always update to the latest available version before troubleshooting sync issues.
Step 3: Check iCloud Drive Is Enabled
Go to: System Settings → [Your Name] → iCloud → iCloud Drive → Options. Ensure iCloud Drive is turned on, and the specific app folders you expect to sync are checked.
Step 4: Force a Sync via Terminal
Open Terminal and run:
brctl log --wait --shorten 2>&1 | head -50This shows real-time iCloud sync activity and error messages. If you see hydration failures or "quota exceeded", those tell you exactly what's failing.
To manually trigger a sync check:
brctl diagnose -d ~/Desktop/icloud_diagThis creates a diagnostic archive on your Desktop that shows the full sync state.
Step 5: Restart iCloud Daemons
Restarting the background iCloud processes resolves the majority of stuck sync issues:
killall birdbird is the iCloud Drive sync daemon. Killing it forces macOS to restart it and re-check sync state. You'll see files briefly show "Waiting" then start syncing.
Also restart the iCloud photos daemon if Photos is affected:
killall cloudd
killall cloudpairdStep 6: Sign Out of iCloud and Sign Back In
This is the most reliable fix for persistent sync failures — it forces a complete re-authentication with Apple's servers:
- Go to System Settings → [Your Name] → Sign Out
- When prompted about keeping iCloud data on your Mac, choose Keep a Copy — this ensures your local files aren't deleted
- Restart your Mac
- Sign back in at System Settings → Sign in with your Apple ID
- Re-enable iCloud Drive in Settings
Allow 15–30 minutes for files to re-sync after signing back in.
Step 7: Reset iCloud Sync Cache
If sign-out/sign-in doesn't help, clear the iCloud sync cache:
# Quit all apps first, then:
killall bird
# Remove the iCloud cache
rm -rf ~/Library/Application\ Support/CloudDocs/session/
# Restart bird
open /System/Library/CoreServices/CloudDocumentSyncAgent.appStep 8: Fix the "Optimize Mac Storage" Conflict
A 2026-specific issue: if "Optimize Mac Storage" is enabled, macOS automatically removes local copies of files to free space. When combined with Time Machine or certain apps, this can cause apparent sync failures where files appear missing locally but are actually stored in iCloud.
To disable: System Settings → [Your Name] → iCloud → iCloud Drive → turn off "Optimize Mac Storage". All iCloud files will then download locally and sync reliably.
Step 9: Check Per-App iCloud Settings
Each app has its own iCloud toggle. If a specific app's files aren't syncing (e.g., Pages, Notes, Reminders), check:
System Settings → [Your Name] → iCloud → Show More Apps → toggle the affected app
Toggle it OFF, wait 30 seconds, then toggle it back ON.
Step 10: Check for Filename Issues
iCloud Drive can't sync files with certain characters in their names: \ / : * ? " < > | — these are invalid on Windows (iCloud syncs cross-platform). Rename any affected files and sync should resume.
Still Stuck? Get Expert Help
If your iCloud Drive is still not syncing after all these steps, CloudHouse Technologies' Pay-Per-Ticket Support has macOS specialists who can diagnose daemon logs, network issues, and Apple ID account problems remotely.