Unlock with Apple Watch on Mac stops working after a day

Apple Watch Unlock on MacBook Air Stops Working After a Day

If you have Unlock with Apple Watch enabled on your MacBook Air, but find that it stops working after approximately a day and requires you to enter your password or use Touch ID again, there are a few things worth understanding.

1. Apple does impose security-related password requirements, but it is important to distinguish between Touch ID and Apple Watch Auto Unlock.

• Touch ID requires your account password after 48 hours without unlocking your Mac, among other security-related circumstances.

• Apple also documents a 156-hour (6.5-day) password requirement under certain additional conditions.

• However, Apple does not document a daily or weekly expiration period for Apple Watch Auto Unlock.

Apple's stated behaviour is that after manually entering your password following startup, restart, or logout, your Apple Watch should automatically unlock your Mac when it wakes from sleep.

In other words, having to enter your password every day is not an established Apple Watch security requirement.

Apple references:

• Use Touch ID on Mac

• Apple's Biometric Security Requirements

• Unlock your Mac with Apple Watch

2. Check your Apple Watch and Mac settings

Make sure that:

• Wi-Fi and Bluetooth are enabled on both devices.
• Both devices are signed into the same Apple Account.
• Two-factor authentication is enabled for your Apple Account.
• Your Apple Watch has a passcode, is unlocked, and is being worn.
• Your Apple Watch is close to your Mac.

3. Reset the Apple Watch Auto Unlock connection

Apple recommends the following troubleshooting procedure:

1 On your Mac, open System Settings >> Touch ID & Password.

2 Find the Apple Watch section and turn off the option to unlock your Mac with your watch.

3 Restart your MacBook Air.

4 Return to the same settings and turn Apple Watch unlocking back on.

5 Test whether the feature continues working over the next several days.

4. Check for software updates

Make sure both macOS and watchOS are running their latest available versions. If this problem began after a recent software update, it could be related to an Auto Unlock software or connectivity issue.

Also, check whether your Mac is unexpectedly restarting overnight. Any restart requires you to enter your password manually at the next login.

5. What if the problem continues?

If you still need to enter your password every 24 hours or so, despite having successfully unlocked your Mac in between, I would suspect an Auto Unlock reliability issue rather than a normal Apple security timeout.

Unfortunately, Apple does not provide a setting to extend the Auto Unlock authentication interval.

You can also consult Apple's troubleshooting instructions here:

Apple Support – Unlock your Mac with Apple Watch

Bottom line: Apple Watch Auto Unlock is designed to continue working when your Mac wakes from ordinary sleep, without requiring daily password authentication. There is no documented 24-hour expiration rule or user-adjustable timeout. If the feature stops working after approximately one day, it is worth investigating as a potential macOS, watchOS, or connectivity issue rather than accepting it as normal behaviour.

That's a good question, and I should clarify the distinction.

Yes, Touch ID and Apple Watch Auto Unlock are two separate authentication methods, although both operate within Apple's overall security framework.

Here's how to understand the requirements:

• 48 hours: If you haven't unlocked your Mac for more than 48 hours, Apple requires you to enter your account password rather than relying on Touch ID.

• 156 hours (6.5 days): Apple also documents a password requirement when 156 hours have elapsed since the last password entry and biometric authentication hasn't been used within the preceding four hours.

However, these are documented biometric security requirements, not a published expiration schedule for Apple Watch Auto Unlock.

Apple's documentation specifically states that after manually entering your password following startup, a restart, or logout, your Apple Watch should subsequently unlock your Mac when it wakes from ordinary sleep.

Therefore, I would not expect you to have to enter your password every 24 hours simply because you're using Apple Watch Auto Unlock.

Unfortunately, Apple doesn't specify a separate maximum period during which Apple Watch Auto Unlock remains available, so I wouldn't want to promise that it will necessarily work for 6.5 days.

My recommendation: Continue with the troubleshooting steps outlined earlier. If you consistently encounter this problem after approximately 24 hours, even though your Mac hasn't restarted or logged you out, I would investigate it as a possible Auto Unlock reliability issue rather than assume it is a normal security requirement.

For reference, Apple's documentation is here:

Apple – Unlock your Mac with Apple Watch

Apple – Biometric Security Requirements

I hope that clears up the distinction!

I just wanted to follow up that following the steps to turn off Unlock with Apple Watch, restart, then turn it back on appears to have completely solved my problem. Thanks!

The Apple Watch uses the 2.4 GHz band for its Bluetooth communication with your Mac, and Bluetooth is an important part of the Auto Unlock feature.

However, there are two separate things worth distinguishing:

1 Bluetooth communication: Your Apple Watch and Mac use Bluetooth Low Energy (BLE) to detect proximity and establish the conditions for Auto Unlock.

2 Authentication: Apple uses additional security mechanisms to establish that the watch is authorized to unlock the Mac. Simply having a Bluetooth connection isn't sufficient.

Does it use 2.4 GHz?

Yes. Bluetooth operates in the 2.4 GHz ISM band (approximately 2.402–2.480 GHz).

This means that interference from other 2.4 GHz devices can potentially affect Bluetooth reliability, including:

• Wi-Fi networks operating on 2.4 GHz.
• Wireless peripherals.
• Other Bluetooth devices.
• USB 3 devices and hubs that can generate 2.4 GHz interference.

One important distinction: Your Mac's Wi-Fi connection does not necessarily need to be on 2.4 GHz. Bluetooth and Wi-Fi are separate radio technologies, even though they share the 2.4 GHz spectrum.

An important detail about your particular problem

I found something interesting in Apple's technical security documentation.

Auto Unlock actually uses two wireless connections:

• Bluetooth Low Energy (BLE) to discover the devices and establish their secure communication.
• Peer-to-peer Wi-Fi to estimate the distance between the devices.

Apple describes the authentication process as using a mutually authenticated, encrypted protocol, with long-term cryptographic keys established when Auto Unlock is enabled. 

This is important because it means that a problem with Auto Unlock isn't necessarily a Bluetooth interference problem.

Why does it stop working after approximately one day?

I couldn't find an Apple documented setting that controls how frequently Auto Unlock must be reauthenticated.

In fact, Apple's current documentation says that after the initial password entry following a restart or logout, the Mac should unlock automatically when awakened, without specifying a daily expiration. 

My suspicion is that you're experiencing a failure in the Auto Unlock authentication mechanism, rather than an intentional security timeout.

Thanks! This is all great info, even though it seems it doesn't include something I can clearly do to solve my problem. I'll try the suggestions you provided.

One question, you said:

Touch ID requires your account password after 48 hours without unlocking your Mac, among other security-related circumstances.

So, is that NOT related to the Apple Watch unlock at all? That is, if everything was working as designed, I should be able to use Apple Watch to unlock up to 6.5 days but trying to use Touch ID will require a password after 48 hours?

Thanks, will do. I re-did the Unlock with Apple Watch as you described yesterday. So far it is working as expected. We'll see what happens later today and tomorrow.