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How to Lock Your Laptop Screen While Using an External Monitor (Windows)

Hooking a laptop up to an external monitor is the most common multi-screen setup in the world. And the most common complaint about it is the same one in every Reddit thread and forum post: I want to use the big monitor and turn off the laptop screen, but Windows either turns off everything or behaves weirdly when I close the lid. Here's what's actually going on and three real fixes.

The three things you might actually want

Before fixing anything, decide which of these you really want — they're different:

• Show on external only. Use the external as your single display; the laptop screen goes black. Best for desk docks.
• Close the lid, keep external on. You want the laptop to act like a desktop tower with the lid closed. Best for ultraportables that get tucked away.
• Lock the laptop screen for privacy, keep external active. The laptop screen has private content; the external has shared content (a presentation, a video). This is the use case ScreenBlind exists for.

Fix 1 — "Show only on 2" (the easy one)

Windows has a built-in projection mode that does exactly the "external-only" thing.

1. Press Win+P.
2. Pick Second screen only from the pop-up panel on the right.
3. The laptop's built-in display turns off; the external monitor takes over.

That's it. To bring the laptop screen back, press Win+P again and choose Extend or Duplicate. Useful for presentations from a projector, when you don't want the laptop screen mirroring confidential notes.

Fix 2 — Close the lid, keep using the external

By default, Windows interprets closing the lid as "sleep." That's almost never what you want when an external monitor is plugged in. Change it once and forget about it:

1. Open Control Panel → Hardware and Sound → Power Options.
2. Click Choose what closing the lid does on the left.
3. For both "On battery" and "Plugged in," set When I close the lid to Do nothing (or only on Plugged in if you'd rather it sleep on battery).
4. Save changes.

Now you can close the lid and the external display keeps running as if the laptop is a desktop PC. Pair this with Fix 1 (Win+P → Second screen only) and you've got a clean, single-monitor experience from a closed laptop.

A practical tip: if your laptop runs hot under load, lid-closed mode can trap heat. Either prop the lid open slightly or set a fan profile in your laptop's vendor utility.

Fix 3 — Lock just the laptop screen, keep the external monitor active

This is the trickier scenario. You want the laptop screen on (so the lid is open, the keyboard/trackpad work, multiple workspaces stay arranged) but the screen content needs to be hidden from view because you're sitting in a public space — a cafe, a coworking desk, a meeting room — and the external is doing the work you actually want visible.

Windows can't do this on its own. Win+L locks the whole session, external monitor included. Win+P "Second screen only" doesn't lock the laptop — the cursor can still wander onto where its screen used to be.

The answer is a selective screen lock. ScreenBlind ticks the laptop's built-in display, leaves the external unticked, and hits Lock Now. The laptop screen turns into a password-protected lock surface with a roaming clock. The external keeps your presentation, your video call, your dashboard, exactly as it was. Cursor clipping means the mouse stays where it should.

Full walkthrough: How to lock one monitor on Windows.

What about when you walk away from the desk entirely?

Different problem, different tool. Use Win+L. That's what the Windows lock is for — leaving for an hour, lunch, end of day. Selective lock is for the short "stepping away but not leaving" windows.

For more on combining the two: Why no app can block Win+L (and why pairing is the right pattern).

Common pitfalls and how to avoid them

• Windows rearranges everything when the external disconnects. Plugging and unplugging shuffles window positions. Apps like DisplayFusion remember layouts; Windows 11's "Remember window locations" setting (Display settings → Multiple displays) helps a lot.
• The laptop sleeps the moment the dock disconnects. If it's a Thunderbolt dock, check vendor drivers — the eject behavior is sometimes configurable.
• HDR / refresh-rate mismatches. Set the laptop screen and external to compatible refresh rates if you see flicker; mixed HDR/SDR sometimes causes weird brightness shifts when one display goes off.
• External monitor only goes black, not "off." That's normal for software-based hiding. To fully power down the panel, use the monitor's power button.

Related reading: Multi-monitor privacy in a shared office · Lock your screen without pausing a video.