Fix: MacBook sleeps at lid closing when on power

If you’re using a recent MacBook you may find that various suggestions found on the web on how you’d keep it from sleeping when you close its lid while on power (especially if you want to have it display only on an external monitor) are obsolete.

There seems to exist an opensource kernel extension (and other similar tools) called NoSleep, working mostly for Intel CPUs (unless you compile from source), but why waste CPU cycles when there is an option for that (probably added more recently by Apple)?

Just go to Settings / Monitors and press Advanced… button (the one at the bottom left in the Greek screenshot below).

At the advanced options popup just turn off the last switch, the one that prevents automatic transition to sleep mode when external power-source is connected and the monitor gets deactivated. Now connect a monitor, an external keyboard and a mouse/trackpad and close that lid without worries.

This should also be useful if you want to keep your MacBook live for an extended time to download something big, but don’t want your MacBook internal keyboard and screen to gather unnecessary dust by being kept open, nor want your system to sleep and pause downloading when your external screen eventually gets deactivated due to perceived inactivity.