How to Lock a Mac During a Presentation or in a Classroom So the Slides Stay on the Projector and Nobody Can Touch Anything

A teacher steps out of the room for two minutes and comes back to find the projector showing a browser, a student's playlist and, on one memorable occasion, the grade book. A conference speaker leaves the laptop on the lectern during the coffee break and returns to a Slack notification that the whole room read. A trainer sets a video running for a workshop and spends the next eight minutes guarding the keyboard instead of walking the room. The problem in each case is the same: a Mac that is driving a screen other people can see has to stay unlocked and awake, and an unlocked Mac is an invitation. This post is about locking a Mac during a presentation or a class so the slides or video stay on screen, nobody can touch anything, and you can still get back in with a fingerprint.

Why the built-in options fall short in a room

macOS gives you a lock screen and a screensaver, and both are designed for an empty office. The lock screen (Control-Command-Q) blanks the display, which on a projector means the room is staring at a black rectangle or your lock-screen wallpaper. A screensaver with a password does the same a few minutes later. Hot corners, Keynote's presentation mode and "prevent sleep" tools keep the picture up, but they do nothing about the keyboard: anyone can press Escape, hit Command-Tab, or open Spotlight. Disabling the keyboard with a third-party tool leaves the trackpad alive and every other app reachable.

What a presenter actually wants is three things at once: the chosen app stays visible and awake, every other app is hidden, and all input is blocked until you say otherwise. That combination is what VibeLock does, and it was built for a different audience (developers leaving Claude Code running on a visible screen), which turns out to be the same problem with a different app on screen.

How VibeLock handles a presentation

VibeLock sorts every app on the Mac into one of three buckets while it is engaged, chosen per app from the menu bar. Visible apps stay on screen so people can watch them, but every keystroke, click and scroll aimed at them is swallowed. Accessible apps can be used while locked, in that app only; marking an app accessible makes it visible automatically, and the list is empty by default. Everything else is hidden behind an opaque backdrop the moment you lock, kept hidden if it tries to come back, and covered by the shield on every Space. The display stays on, so the projector keeps showing whatever you left there.

For a presentation you mark the slide or video app as Visible (or Accessible, see below) and lock. The room sees the slides. A student who wanders up and presses a key gets nothing; a click on the menu bar or a key press in a non-accessible app brings up the unlock shield instead. Spotlight (Command-Space), Force Quit (Command-Option-Escape) and Command-Q are blocked system-wide, VibeLock refuses to quit, and a watchdog re-arms the input firewall if macOS ever disables it. To get back in, use Touch ID or type your Mac login password into VibeLock's own shield; it is verified locally through macOS and nothing is stored or sent anywhere.

Three ways to set it up, depending on who needs to touch it

1. Self-running content: Visible only

A video, a looping slideshow, a timer, a live dashboard during a workshop exercise. Mark the player Visible, start it, lock. Nobody can pause it, skip it, or switch to anything else, and the screen stays awake for as long as it runs. This is the same setup as keeping a video playing on a locked Mac, pointed at a projector instead of a sofa.

2. You present, you step away: Visible, unlock to advance

For slides you advance by hand, lock whenever you leave the lectern (a break, a group exercise, a quick trip to find the HDMI adapter) and unlock with Touch ID when you are back. The slide you were on stays up the whole time; nothing else is reachable. Unlocking is one fingerprint, which is fast enough to do a dozen times in a session.

3. Someone else needs to drive one app: Accessible

A student presenting their own slides on the class Mac, a co-host clicking through a demo, a colleague who should be able to advance Keynote and nothing else. Mark that one app Accessible: key presses reach it when it is frontmost, clicks and scrolls reach its windows, and Command-Tab is allowed so they can switch between accessible apps. Clicks on everything else are swallowed, and even an accessible app cannot be quit, because Command-Q stays blocked across the board. This is the same mechanism described in letting a colleague approve an agent prompt without unlocking the Mac.

Practical notes for projectors and classrooms

• External displays and Spaces. Visible apps work across all Spaces and displays, so a mirrored or extended projector shows what you expect. If a blocked app has a fullscreen window on another Space, it stays where it is but is covered by an opaque shield if anyone swipes to it.
• Notifications. VibeLock hides apps; it is not a Do Not Disturb switch. Turn on a Focus mode before you lock so Slack and Messages do not appear on the big screen.
• Presenter display. If your slide app uses the laptop screen for notes and the projector for slides, both are windows of the same Visible app and both stay up. Decide whether you are happy for the room to see the laptop if they walk past.
• Accessibility permission. Input blocking needs the macOS Accessibility permission; VibeLock asks for it on first lock. Grant it before the session, not in front of the room.
• Touch ID on a closed lid. If the MacBook is in clamshell mode on a lectern, Touch ID is unavailable, so you will unlock with your password on the shield. Keep the lid open if you want the one-touch unlock.

When not to use it

VibeLock is a lock for a Mac you will come back to, not a kiosk manager. If the Mac is going to run unattended for a day in a lobby or a trade-show stand, macOS's own single-app or managed kiosk setups are built for that and survive restarts; the comparison is in Guided Access for Mac. And if the person at the keyboard should have full use of the Mac (a shared classroom machine during the lesson), locking it is the wrong tool; log them in as a separate user instead. Marking Terminal or a browser Accessible also deserves a pause, because an accessible terminal gives anyone at the keyboard a shell, and an accessible browser gives them the web; keep the accessible list to the one app the room needs.

The thirty-second routine

• Before the session: grant Accessibility, pick a Focus mode, mark your slide or video app Visible (or Accessible if someone else drives).
• Start the slides or the video, make sure the projector shows them.
• Lock from the menu bar whenever you leave the laptop.
• Come back, touch the sensor, carry on from the same slide.

The result is a Mac that behaves like a television for everyone except you: the picture stays up, the room cannot change the channel, and the remote is your fingerprint.