How to Auto-Lock Your Mac the Moment You Walk Away

The problem with manual locking

Your Mac sits unlocked on the desk. You step away to grab a coffee, chat with a colleague, or join a meeting. Minutes pass. When you return, anyone with access to your desk can see everything on screen: email, browser history, spreadsheets, client work, messages. You might have opened sensitive files without thinking to lock. The habit of manually locking your screen every time you leave is exhausting and easy to forget.

The inactivity timer on your Mac is a partial answer, but it misses the reality of modern work. Set it to lock after five minutes and you get locked out of a call or a deep focus session mid-way. Set it to lock after 30 minutes and it defeats the point; a wanderer could have your screen for a long time. The lock is reactive, not predictive. It locks based on keyboard and mouse inactivity, not on whether a human body is actually there.

Hot corners (moving your mouse to screen edge to trigger a lock) are manual and fragile. Quick menu-bar buttons require a deliberate click. Neither solves the core problem: how do you know when to lock without thinking about it?

How on-device presence detection works

The most practical solution is to detect your presence in real time using signals that are already available on your Mac: your camera and, optionally, your Apple Watch. The key insight is that presence detection does not require identification. Your Mac does not need to know who you are; it only needs to know whether a face is visible in frame.

Apple's Vision framework, built into macOS, can analyse camera frames locally to detect whether a face is present. This processing happens on your Mac; the camera feed never leaves it. No image is saved or transmitted. The system simply answers one question, 20 times per second: is a face in view right now?

If your Apple Watch is nearby and connected via Bluetooth, the Mac can cross-check: Watch present and face present means you are at your desk. If the Watch signal drops (you walk away) or the camera stops seeing a face, the departure is clear. Add keyboard and mouse activity as a third signal, and the system avoids locking you during a hands-free call or a moment when you are looking away temporarily.

The combination of these three signals on-device face presence, optional Apple Watch proximity, and input activity creates a robust picture of your presence without cloud processing, without an account, and without any data leaving your Mac.

What Peeku does

Peeku is a Mac app that implements this approach. It runs as a menu-bar accessory and displays your presence signals live so you can watch them and trust them before you arm the lock. Once armed, Peeku monitors the three signals continuously. When all of them agree that you have left the desk, it locks your screen in real time using the standard macOS screen-lock command.

The auto-lock is available in the full version of Peeku, which is a direct download outside the App Store. This is because Apple's sandboxing prevents App Store apps from invoking system-level locking commands. The full Peeku app is Developer ID signed and notarised by Apple, which means Apple has verified the developer identity and scanned the code for known malware.

Setup in two minutes

Getting Peeku working requires three straightforward steps.

1. Enable camera access

Peeku needs to access your Mac's built-in camera to detect face presence. On first launch, macOS will prompt you to allow camera access. Grant it. If you have denied it in the past, you can re-grant it in System Settings: go to Privacy and Security > Camera, find Peeku in the list, and toggle it on.

2. Set "Require password immediately"

Open System Settings and navigate to General > Lock Screen. Find the setting "Require password after sleep or screen saver" and set it to Immediately. This ensures that when Peeku locks your screen, macOS will demand your password to unlock. Without this setting, the screen lock has no security value; anyone can press a key to regain access. If you have enabled this and your Mac still will not lock on its own, the guide to fixing a Mac that will not lock automatically works through the most common causes.

3. Toggle auto-lock in Peeku

Open the Peeku menu-bar panel (click the icon in your menu bar). You will see your face presence, Watch status, and input activity displayed live. Before arming, watch these signals for a moment to build trust. When you are confident, toggle the "Auto Lock" switch to on. Peeku is now armed and will lock when all signals agree you have left.

If you use an Apple Watch, pair it in Peeku's settings for optional proximity gating. Without a Watch, Peeku still works perfectly using face presence and input activity alone.

Real-world scenarios

Privacy and the on-device guarantee

A natural question: how do I know my camera processing is truly local? The answer is in Peeku's design. The app requires no account, no sign-in, no cloud service. You can disable internet on your Mac and Peeku still locks your screen. All face presence detection runs inside the macOS Vision framework, which is part of the operating system. Your camera feed is never saved to disk and never sent to any server. You can verify this by checking your Mac's network traffic with a packet sniffer if you wish.

For more detail, see Peeku's privacy page, which explains the exact signals used and how they are processed on device.

When to use auto-lock

Auto-lock is practical for anyone who leaves their desk unattended, even briefly. It is especially valuable in shared spaces, offices with traffic, and homes with family or housemates. For very sensitive work (reviewing documents you cannot expose, handling credentials, analysing client data), auto-lock becomes a helpful security habit, complementing other practices like strong passwords and two-factor authentication.

It is not a substitute for full encryption or endpoint security, but it is a simple, on-device step you can take right now.

How detection is tuned for real life

Peeku does not lock on the first frame where a face disappears; it waits for a few seconds to ensure you have actually left, not just looked away or blinked. The wait time is short enough to be practical: a moment to lock is not noticeable, but it avoids false locks during a brief turn of the head. If you have Apple Watch nearby, Peeku can add a proximity gate so the lock requires both the Watch signal and the face signal to drop, reducing accidental locks further.

The system also respects input activity. If your keyboard or mouse is still active, Peeku assumes you might return in a moment and does not lock. This is crucial for hands-free calls where you are speaking but not touching the keyboard, or for moments when you are referencing notes off-screen.

Getting started

Download Peeku from Gumroad or via direct DMG. It is free, pay-what-you-want on Gumroad, or a direct instant download. The app is Developer ID signed and notarised, so it is safe to run. If you are not sure how exposed your current setup is, start with the free Mac lock risk checker. Once installed, open it, grant camera access, set your Mac to require a password immediately, and toggle auto-lock on. Watch the signals for a moment, step away from your desk, and confirm the lock engages as you leave.

For more on how detection works, see the guide on Mac camera privacy myths. For wellness coaching alongside auto-lock, learn about the 20-20-20 eye rest rule, which Peeku can nudge you to follow, or see how the Mac eye-break and posture apps compare.