Windows 10: How to Lock (not sleep) laptop on lid close?

As far as I know, there is no built-in function to achieve this. But you can do this using a third party tool.

One of them is LapLock. This program is a lightweight (<50KB), open source tool and it's developed by Etienne Dechamps.

Steps...

1. Download the program - https://github.com/dechamps/laplock/releases
   ^{(Download the latest laplock.exe release)}

2. Open the Windows Startup folder by using this run command - 'shell:common startup'

3. Add laplock.exe to your Startup folder.

You can also use Lid Lock to do this.

Set "Do Nothing", lock your laptop using Windows key+L, and then you can close the lid.

Two steps:

• Capture the close lid event.
• Trigger a lock-screen event.

See: Capturing laptop lid closing event in windows?, and Command-line (cmd) command to lock a windows machine.

From those sources, we can use RegisterPowerSettingNotification and GUID_LIDSWITCH_STATE_CHANGE to detect the trigger, and run:

rundll32.exe user32.dll,LockWorkStation 

from the command line to send a lock screen request to the machine.

I don't know what compilers you have available, or what languages you know, but this information should help you set up a program to do it for you.

I don't use Windows myself, so I can't build or test it for you.