How to Lock One Monitor on Windows (and Keep the Other On)
If you've ever wanted to lock just your laptop screen while the external monitor keeps a presentation running — or hide your second display while your main one stays usable — you've probably already discovered that Windows can't do it natively.
Win+L is an all-or-nothing switch. It locks the entire session. Every monitor goes to the Windows lock screen, every app you had open is hidden, and anything that was playing — a webinar, a Twitch stream, a digital signage dashboard — gets covered up along with everything else.
For a lot of multi-monitor workflows, that's the wrong tool. You don't want to end the session; you want to hide a specific screen. This article walks through why Windows works the way it does, and the lightweight workaround that actually solves the problem.
Why Windows can't lock a single monitor
The Windows lock screen is a session-level feature. When you press Win+L, the OS pivots the whole user session into a "locked" state — desktop access is suspended, and the secure lock screen takes over every connected display. There's no setting to lock "monitor 2 only" because, from Windows' perspective, all your monitors are showing facets of the same one session.
Group Policy doesn't help. Neither does any registry tweak. You can hide a specific monitor with a third-party tool, send a black image to it, or change its input — but those aren't locks. They don't capture input, they don't prompt for a password, and anyone with mouse access can flip them off in a second.
The actual workaround: a selective-lock overlay
The pattern that works is a small user-mode application that draws a password-protected overlay window on top of just the monitors you choose — leaving the others completely untouched. The locked screens look like a normal lock screen (clock, background, idle screensaver), and they capture mouse and keyboard input directed at them so you can't click "through" the lock. The unlocked screens behave exactly as before.
That's what ScreenBlind does. It's a free Windows app (10 and 11) designed for one purpose: locking the monitors you pick while leaving the rest of your desktop visible and active. Below is how to use it.
Step 1 — Open ScreenBlind
Download the .exe and double-click to run it. There's no installer — it's a single file under 40 MB. The first time you open it, ScreenBlind sits in your system tray and the main window pops up with two tabs: Monitors and Security.
Step 2 — Tick the screens you want to lock
Every connected display is listed in the Monitors tab with a name, resolution, and a checkbox. Tick the ones you want covered.
A common setup: in a three-monitor layout, you lock your laptop screen and the side monitor (which has your email, Slack, and personal stuff on it) and leave the center monitor unchecked — that's the one running your slide deck, video call, or dashboard.
Step 3 — Set a password (once) and hit Lock Now
The Security tab is where you set the password. ScreenBlind hashes it with PBKDF2-SHA256 and stores only the hash on your machine — no plaintext, no cloud, no telemetry. After that, "Lock Now" turns the selected screens into a dim, animated lock surface. A roaming clock, a screensaver (Bubbles, Matrix rain, or your own slideshow), and the password prompt are all you'll see on the locked displays.
On the unlocked screens, nothing changes. Your video keeps playing. Your dashboard keeps updating. Your meeting keeps recording.
What the locked screens actually do
- Capture input. If you move the mouse onto a locked screen, the cursor stays there until you unlock — it can't slide through to a different monitor and bypass the lock.
- Block the Windows key. Pressing Win on a locked screen doesn't open Start.
- Prompt for the password. Mouse or keyboard activity on the locked screens brings up a password box. Wrong password? It shakes. Right password? Every locked screen unlocks at once.
- Stay alive. The clock drifts around and an idle screensaver kicks in, so the locked screen never looks static and there's no burn-in risk on OLEDs.
What ScreenBlind can't do
Being honest about this matters. ScreenBlind is a user-mode privacy tool — not a replacement for the OS lock screen — and there are two shortcuts no third-party app on Windows can block:
- Win+L is handled by the Windows kernel before any app sees the keypress. Pressing it still triggers the system lock screen.
- Ctrl+Alt+Del is the Secure Attention Sequence, intentionally untouchable by software.
If someone presses either, they end up on the Windows lock screen. They'd have to enter your Windows password and your ScreenBlind password to actually see the locked monitors — which, in practice, is stronger than either lock alone. We have a longer explainer on this: Why no app can block Win+L on Windows.
When this workflow shines
Some of the situations where locking one screen — but not all of them — is exactly the right move:
- Stepping away from a presentation, demo, or webinar without ending the session. See: Lock your screen without pausing a video or stream.
- Working in a shared office where your second monitor faces a hallway. See: Multi-monitor privacy in a shared office.
- Running an OBS broadcast, trading dashboard, or wall-mounted info screen that needs to stay visible while you're away. See: AFK screen lock for streamers, traders, and dashboard users.
That's the entire pattern. Three clicks, one password, screens you choose. The rest of your desktop keeps doing what it was doing.