Apple - Preventing MacBook from sleeping when closing lid on Sierra
InsomniaX works perfectly on my MBP 13" 2015. I am using macOS Sierra 10.12.
There's also an app called NoSleep, but it hasn't been updated in years, only use it if you're on older OSX like Mavericks or Yosemite.. I wouldn't recommend using it on Sierra..
UPDATE: 1st FEB, 2020 InsomniaX is not being mantained anymore & you SHOULD NOT use it. No sleep is a better option until MacOS Mojave. Haven't tested any of these with MacOS Catalina. If anyone has tested with Catalina, let us know in the comments.
Amphetamine (Free, App Store)
Currently, the best option for modern macOS versions is Amphetamine. This is a free utility that can keep your screen awake, prevent your computer from sleeping when the lid is open, and prevent your laptop from sleeping when the lid is closed.
This is the best option over the other alternatives mentioned because:
- It is free
- It is compatible with macOS versions back to 10.11 El Capitan, and likely will be updated for macOS Big Sur soon after it is released (not sure if it works already)
- It is updated frequently
- As for keeping your laptop awake with the lid closed, you may install an optional helper tool which "adds a fail-safe for the closed-display mode," increasing the reliability of lid-close-sleep-prevention feature. The helper tool is also open source
- It is readily available on the macOS App Store.
Tested NoSleep 1.4.0 on my MacBook Air 2012 and it works with macOS High Sierra 10.13.0. Simply need to authorize the use of NoSleep kext in Security settings when warned during install.