Why Your Mac Is Not Locking Automatically, and How to Fix It

What "auto-lock" actually means on a Mac

There is a common misunderstanding worth clearing up first. macOS has no built-in feature that locks the screen the moment you physically leave your desk. It cannot tell that you have walked away; it only counts how long there has been no keyboard or mouse activity. What people call "auto-lock" on a Mac is really two separate settings working together:

• An inactivity timer that starts the screen saver or turns the display off after a chosen number of minutes of no input.
• A password requirement that decides whether macOS asks for your password once the screen saver has started or the display has turned off.

If either of these is set wrong, your Mac will appear not to lock. The display might dim but stay unlocked, or it might never sleep at all. Locking by hand with a keyboard shortcut is instant, but it depends on you remembering to do it every single time. The rest of this guide walks through each cause in order.

The setting that decides whether locking is secure

This is the single most common reason a Mac "does not lock". Even when the screen saver starts, macOS will not require a password unless you have told it to, and by default it often allows a short grace period during which anyone can wake the Mac without a password.

Why the screen saver or display never starts

The second common cause is that the inactivity timer is too long, switched off, or being held awake by something. macOS only begins the screen saver or display sleep after the idle period you have configured, so check these in order.

• The timer is set to a long interval or to Never. In System Settings, under Lock Screen, look at "Start Screen Saver when inactive" and the "Turn display off when inactive" options for battery and power adapter. If these are set to a long time or to Never, the Mac will sit awake and unlocked indefinitely. Choose a short interval you are comfortable with, such as one to three minutes.
• Something is keeping the display awake. Playing video, a presentation in full screen, a keep-awake utility, or the caffeinate command in Terminal can all stop the screen saver and display sleep from ever triggering. Quit anything that holds the display on when you step away, or, if you are deliberately keeping the Mac awake for a long job, lock the screen by hand without putting the Mac to sleep.
• Sleep is being prevented on power. In System Settings under Battery, an option to prevent automatic sleeping while the display is off can keep the Mac active. Review it if your Mac never sleeps when plugged in.

For a fuller comparison of every locking method, from the native timer to Bluetooth proximity and camera presence, see the guide on ways to auto-lock your Mac in 2026. If you want a quick read on your own setup first, use the free Mac lock risk checker.

Lock your Mac instantly, by hand

While you sort out the automatic settings, it helps to know the fastest manual locks. Each of these works on any modern Mac and locks immediately, provided the password requirement above is set to "Immediately".

• Keyboard shortcut: press Control and Command and Q together to lock the screen instantly.
• Apple menu: click the Apple menu in the top-left corner and choose "Lock Screen".
• Hot corner: in System Settings under Desktop & Dock, open Hot Corners and assign a corner to "Lock Screen". Pushing your pointer into that corner then locks the Mac in one move.

These are reliable, but they share one weakness: they depend on you remembering to do them every time you get up. On a busy day, or when you are pulled away mid-thought, that is exactly the moment the habit fails.

The gap a timer cannot close

Even with everything configured correctly, the native approach is fundamentally time-based, not presence-based. macOS counts idle seconds; it does not know you have left. That leaves a gap. Set the timer to one minute and your screen stays open for up to a minute after you walk away. Set it to ten seconds to feel safer and it will nag you with a black screen every time you pause to read or think. There is no idle interval that is both quick to lock when you leave and patient while you stay.

Presence detection closes that gap by answering a different question: not "how long has it been idle?" but "is the person still here?". This is the approach Peeku uses to auto-lock the moment you walk away. Peeku combines three local signals to decide you have actually left:

• Face presence from the built-in camera, analysed on your Mac with Apple's Vision framework. No image or video leaves the device.
• An optional Apple Watch proximity gate over Bluetooth, so the Mac only locks when both the camera and the Watch agree you are away. The Apple Watch reinforcement guide covers pairing and how that gate works.
• Keyboard and mouse idle time, used to avoid locking during a brief pause.

When the signals agree you have gone, Peeku locks within a few seconds, and because it waits for genuine absence rather than a fixed timer, it does not lock you out while you sit reading. Detection runs entirely on your Mac, with no account and no cloud face data; you can read how that works in the guide on privacy-first, on-device auto-lock. One honest caveat: the full locking app ships free outside the Mac App Store, on Gumroad and as a notarised DMG, because the App Store sandbox blocks the system screen-lock calls. And it still relies on the "Require password: Immediately" setting above, so configure that first either way.

A quick checklist

If your Mac is not locking the way you expect, run through this in order:

1. System Settings, Lock Screen: set "Require password after screen saver begins or display is turned off" to Immediately.
2. Same pane: set "Start Screen Saver when inactive" and the display-off options to a short interval, not Never.
3. Quit anything keeping the display awake (video, presentation mode, keep-awake utilities, caffeinate).
4. Learn the instant manual lock: Control + Command + Q, or a Hot Corner set to "Lock Screen".
5. If you want the lock to happen the moment you leave, rather than after a timer, add presence detection. The two-minute setup is covered in the guide on setting up walk-away lock.