Fix Apple Watch Not Unlocking Mac in macOS Big Sur

If your Apple Watch stops unlocking your Mac after upgrading to macOS Big Sur, the fix is usually to re-enable the feature in System Preferences and ensure both devices meet the continuity requirements. Start by going to System Preferences > Security & Privacy > General and checking “Allow Apple Watch to unlock your Mac,” then sign out and back into iCloud on the Mac if it still fails.

Why the Feature Exists and How It Works

Apple introduced “Unlock with Apple Watch” in macOS Sierra as a convenience feature for Macs with a T-series security chip or Apple silicon. When your Mac wakes from sleep or the display turns on, it uses Bluetooth to detect a paired, unlocked Apple Watch worn on your wrist. The watch then sends a cryptographic handshake to the Mac, which unlocks the login session without requiring a password.

On macOS Big Sur, the feature depends on several simultaneous conditions: both devices must have Bluetooth and Wi-Fi enabled, the Mac must have “Allow Apple Watch to unlock your Mac” checked, the watch must have a passcode and wrist detection enabled, and both devices must be signed into the same Apple ID with two-factor authentication. If any of these is off, the unlock silently fails.

Prerequisites Before Troubleshooting

Before diving into fixes, verify that your hardware and software actually support the feature. Unlock with Apple Watch requires a Mac from 2013 or later (with the exception of the 2013 Mac Pro) and an Apple Watch Series 1 or later. On Big Sur, the Mac must also have Bluetooth 4.0 or later and be signed into iCloud with the same Apple ID as the watch.

Mac model: 2013 or newer (check Apple menu > About This Mac)
macOS version: Big Sur 11.0 or later (Apple menu > About This Mac > Software Update)
Apple Watch: Series 1 or later with watchOS 7 or later
Both devices: Bluetooth and Wi-Fi turned on
Both devices: signed into iCloud with the same Apple ID and two-factor authentication enabled

If you have an older Mac without a T2 chip or Apple silicon, the feature still works, but it may be less reliable because it relies entirely on Bluetooth LE rather than the secure enclave on newer chips.

Step-by-Step Fix for Big Sur

Follow these steps in order. Most users resolve the issue at step 1 or 2.

Re-enable the setting: Go to System Preferences > Security & Privacy > General. Uncheck “Allow Apple Watch to unlock your Mac,” wait 10 seconds, then re-check it. You may need to click the lock icon and enter your password first.
Restart both devices: Restart your Mac and your Apple Watch (press and hold the side button, then drag the power off slider). After they reboot, try locking your Mac (Apple menu > Lock Screen) and waking it.
Check Bluetooth and Wi-Fi: On the Mac, open System Preferences > Bluetooth and ensure it’s on. Also check Wi-Fi is connected to a network. On the watch, swipe up to Control Center and confirm Bluetooth and Wi-Fi icons are blue (not gray).
Sign out and back into iCloud on the Mac: Go to System Preferences > Apple ID > Overview. Click Sign Out, then sign back in with the same Apple ID. This refreshes the continuity handshake. Note: signing out may remove some local data like Keychain items, so back up first.
Reset the watch’s pairing (last resort): On the watch, go to Settings > General > Reset > Erase All Content and Settings, then re-pair it with your iPhone. This is time-consuming but fixes persistent sync issues.

After each step, test by locking the Mac and waiting 5 seconds before waking it. If it still doesn’t unlock, move to the next step.

Common Problems and Their Specific Causes

Users on Big Sur often report three distinct failure modes. First, the Mac never shows the “Unlocking with Apple Watch” message – this usually means the Bluetooth connection is not established or the setting is off. Second, the message appears but the unlock fails – this points to a stale iCloud session or a watch that is not actually unlocked. Third, the feature works once then stops – this often happens after the watch charges overnight or after a macOS update resets the preference.

Another frequent issue is that the Mac requires a password after the watch is used for Apple Pay or after the watch has been off the wrist for a while. This is by design: wrist detection must be on, and if you take the watch off, the Mac will not unlock until you re-authenticate. Also, if you’re wearing gloves or the watch is under a sleeve, the wrist detection sensor might not register, causing intermittent failures.

What to Do If the Setting Is Grayed Out

If the “Allow Apple Watch to unlock your Mac” checkbox is grayed out, the Mac does not detect the watch as eligible. This usually happens because the Mac lacks the required hardware (pre-2013 model) or because the watch is not signed into the same Apple ID. Check that the watch is paired to your iPhone and that the iPhone is nearby with Bluetooth on. If the watch is new, unpair and re-pair it with the iPhone, then restart the Mac.

On some Big Sur versions, the setting also grays out if the Mac’s Bluetooth hardware is malfunctioning. Try resetting the Mac’s Bluetooth module by holding Shift+Option and clicking the Bluetooth icon in the menu bar, then selecting “Reset the Bluetooth module.” This is a hidden debug option and may require you to re-pair other devices.

Alternative Unlock Methods in Big Sur

If the Apple Watch unlock continues to fail, you have other options. The most reliable is to use Touch ID on Macs that have it, which is faster and doesn’t depend on Bluetooth. For older Macs, you can set up Auto Unlock with a nearby iPhone (if you have an iPhone with Face ID or Touch ID) – though that feature is more limited in Big Sur. You can also simply type your password, but that defeats the purpose.

Some users find that turning off “Automatic Login” in System Preferences > Users & Groups makes the watch unlock more consistent, because the Mac always shows the login screen after sleep. Also, disabling “Require password after sleep” and relying solely on the watch is not recommended for security, but it does avoid the issue entirely.

Security and Privacy Considerations

Unlock with Apple Watch is designed to be secure: it uses a random key that is exchanged over Bluetooth with encryption, and the watch must be unlocked and on your wrist. However, it is not as strong as a password or Touch ID because it only requires proximity, not a biometric check on the Mac. If you are in a public space and your watch is stolen while unlocked, someone could unlock your Mac. Apple mitigates this by requiring the watch to be on your wrist (wrist detection), but that is not foolproof.

For sensitive work, consider disabling the feature when you are away from trusted locations. You can also set the Mac to require a password immediately after sleep (System Preferences > Security & Privacy > General > Require password) and still use the watch for convenience – the watch only bypasses the password prompt, not the initial login after reboot.

Frequently Asked Questions

Why did my Apple Watch stop unlocking my Mac after the Big Sur update? Big Sur changed the continuity handshake and sometimes resets the preference. Re-enable the setting in System Preferences and restart both devices. If that fails, sign out of iCloud on the Mac and sign back in.

Does the Apple Watch unlock work if the Mac is off or restarted? No. The feature only works when the Mac is asleep or the display is off, not after a full shutdown or restart. You must enter your password once after booting up.

Can I use the Apple Watch to unlock a Mac that is not signed into the same Apple ID? No. Both devices must be signed into the same Apple ID with two-factor authentication enabled. If you have multiple Apple IDs, switch to the same one on both devices.

Will the unlock work if my iPhone is not nearby? Yes, the Mac and watch communicate directly over Bluetooth, so the iPhone does not need to be present. However, the watch must have been recently unlocked and have a passcode.

Is there a way to force the unlock to work faster? The unlock typically takes 1-2 seconds after the Mac wakes. To speed it up, ensure the watch is on your wrist and the screen is not covered. Disabling Bluetooth on the Mac or watch will break the feature entirely.

General steps for current mainstream versions; menus can differ by device and version. See the disclaimer or report an error.

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