https://intelliscapesolutions.com/apps/caffeine

Don't let your Mac fall asleep.

Download NowVersion 1.1.3, macOS Yosemite or Later
Compatible with macOS Catalina!
Release Notes  ·  View Source

Caffeine is a tiny program that puts an icon in the right side of your menu bar. Click it to prevent your Mac from automatically going to sleep, dimming the screen or starting screen savers. Click it again to go back. Right-click (or ⌘-click) the icon to show the menu.

Originally developed by Tomas Franzén of Lighthead Software in 2006, Caffeine is a well known and loved utility for many Mac users, and its simplicity has allowed it to continue working perfectly long after active development ceased.

Unfortunately for many users, Caffeine began experiencing problems with the release of macOS Mojave, due to the enhanced privacy controls introduced which prevent Caffeine from functioning correctly.

We reached out to Tomas to inquire if we could continue development of Caffeine, as we believe it fits nicely with our vision of software that is simple, flexible and powerful.

Tomas has graciously provided the source code under an open source license, allowing us to continue developing Caffeine where he left off.