Amphetamine

keep-awake utility for macOS. prevents sleep, screen dimming, and screensaver activation on demand.

lives in the menu bar. click to toggle, or set triggers (while app X is running, while on Wi-Fi Y, etc.).

why not Caffeine: Amphetamine is the spiritual successor — more features, still free, App Store distributed. Caffeine is abandoned.

install: Mac App Store (free)