17 Caffeine / Amphetamine
Seasoned Mac users probably know about Caffeine. It’s long been a staple of “free Mac app” lists. Mac users running newer macOS versions can be the same results in a more updated platform by using Amphetamine.
Basically a stimulant for your computer, both of these apps will override your Mac’s automatic sleep function, as well as screen dimming or screensaver. Amphetamine also prevents your Mac from sleeping when you close the lid, which is particularly handy when your outputting your computer to an external monitor. Either way, both apps are free and work amazingly when you simply when you want your Mac to stay awake.