Key Codes is a little utility that displays the key code, unicode value, and modifier keys state for any key combination you press. If you're a developer, this might be useful to you.
What’s new in version 2.2.1
Updated on Mar 02 2021
Version 2.2.1:
Made the app icon a Big-Sur-style rounded rectangle that also happens to resemble a keyboard key. That's the only change, so if you don't like rounded rectangle icons, you can safely skip this update.