1. Change Energy Saver settings
The most obvious option. Open System Settings, go to Energy Saver (on a desktop Mac) or Battery (on a laptop), and drag the "Turn display off after" slider to "Never." Your Mac won't sleep on its own anymore.
The downside is it's global and permanent until you change it back. If you're on a laptop and forget to revert this, your Mac will stay awake all night and drain the battery. There's no way to say "never sleep, but only on weekdays" or "never sleep, but only when I'm plugged in." It's all or nothing.
Good for: desktop Macs that should always stay on, like a media server or a Mac Mini running Plex.
2. The Hot Corners trick
This one is more of a workaround than a real solution. Go to System Settings, then Desktop & Dock, then Hot Corners. You can assign "Put Display to Sleep" to a corner, but more usefully, you can assign "Disable Screen Saver" to a corner and park your cursor there.
The problem is your cursor has to stay in that corner. Move it and the effect goes away. It's fragile, easy to break accidentally, and not something you can set and forget.
Good for: absolutely nothing, honestly. But people suggest it online, so it's worth mentioning why it doesn't really work.
3. A system-level keep-awake app
Apps like Amphetamine and Lungo sit in your menu bar and prevent sleep using the macOS system API. Click the icon, your Mac stays awake. Click again, normal behavior resumes. Amphetamine is free with a deep trigger system. Lungo is $4 and beautifully simple.
These work well for most people. The limitation is that they operate at the system level, which means your Mac stays awake but isn't generating any real user activity. Remote desktop sessions can still time out. Messaging apps can still mark you as away. And if your IT department has locked sleep settings via MDM, system API calls might be blocked.
Good for: people who want a simple toggle and don't need mouse activity or advanced conditions.
4. A mouse jiggler app
A mouse jiggler moves your cursor at regular intervals to reset the idle timer. macOS sees it as real user activity, which means it works everywhere: corporate environments with locked settings, remote desktop sessions, messaging apps that track your status.
Shake It On is a mouse jiggler that lives in your menu bar. It moves your cursor with smooth, organic motion and has 12+ smart conditions so it only runs when you actually need it. Pause when the camera is on. Pause on battery. Only run on weekdays. Only run when a specific app is open. Set it up once and forget about it.
This is the approach we'd recommend for most people. It combines the reliability of actual mouse movement with the intelligence to know when to stop.