How to kill a process that is a using port on macOS

Every so often I get stuck with a running process that’s using a specific port, preventing me from running some new application that uses the same port. Then I’m left Googling for solutions or rebooting the machine to make progress. But not any more! I’m recording the solution for my future self (and of course for you, dear reader).

> sudo lsof -i :<PortNumber>  # returns list of processes using the port, with PID

> kill -9 <PID>  # kill the specific pid

For example, you can find out what’s running on port number 8080 by running the command:

❯ sudo lsof -i :8080
COMMAND   PID            USER   FD   TYPE             DEVICE SIZE/OFF NODE NAME
java    50693 kevinsookocheff  369u  IPv6 0x861ee023f0aa0b29      0t0  TCP *:http-alt (LISTEN)

lsof returns the PID of the running process that uses the suspect port. You can terminate that process with the kill command:

❯ kill -9 50693

And voilà! The port is free once more!