The spinning rainbow wheel will appear on your computer's screen when macOS detects that your system can't keep up with all of the tasks you're asking it to handle.

What is the Mac spinning wheel? This rainbow-colored spinning wheel appears whenever an app on your Mac needs more time to perform a particular task and becomes unresponsive while doing it.

If the cursor resembles the rainbow spinning wheel, the app is unresponsive. Once you've identified the unresponsive app, locate the taskbar at the top of your screen.

When the spinning rainbow wheel appears on your computer, take solace in the fact there’s an easy way to force quit on your computer, too. First, click out of the unresponsive app.

The spinning rainbow wheel will appear on your computer's screen when macOS detects that your system can't keep up with all of the tasks you're asking it to handle.