How do I fix 'EADDRINUSE: address already in use' when starting my Node.js server?

Node.js/Express app started with npm run dev on port 3000. I previously stopped the server with Ctrl+C (or closed the terminal), then tried to start it again. On Windows 11, but I'd also like to know the macOS/Linux equivalent.

Running npm run dev should start the server and print 'Listening on port 3000'.

The process crashes immediately with Error: listen EADDRINUSE: address already in use :::3000.