Что -то уже работает на порту 3000.
npx kill-port 3000 8080 4200
Xenophobic Xenomorph
npx kill-port 3000 8080 4200
netstat -ano | findstr :3000
taskkill /PID "123" /F
netstat -ano | findstr :3000
taskkill /F /PID PID_of_port
npx kill-port 3000 8080 4200
If this error is in nextjs
in package.json, update scripts:
"dev": "PORT=3001 next dev",
you can choose other port, and also change for start.
$ lsof -i tcp:3000
$ kill -9 PID