Amphetamine

From Mac App Store

Available on Mac

Amphetamine is designed to keep your Mac awake even when it wants to sleep, and you can use it to keep connected displays awake too. You can enable Amphetamine for specific apps or for specific tasks, so for example you might want your Mac to stay awake while you’re using headphones or prevent the main display from going to sleep when a particular app is open. It’s really easy to use but it’s also packed with options and statistics.