How to Kill a Process on a Port on Mac

Step 1: find the PID

lsof -nP -iTCP:8080 -sTCP:LISTEN

Note the number in the PID column.

Step 2: ask it to quit (SIGTERM)

kill 18232

kill without options sends SIGTERM, which lets the program close files and connections cleanly.

Step 3: force it only if needed

kill -9 18232

SIGKILL ends the process immediately and cannot be caught, so unsaved data and temp files are not cleaned up. Use it only if SIGTERM was ignored.

One-liner

kill $(lsof -ti tcp:8080 -sTCP:LISTEN)

-t prints only PIDs. Be careful: if nothing matches, an empty kill fails harmlessly, but if several processes match they are all signalled.

Step 4: verify

lsof -nP -iTCP:8080 -sTCP:LISTEN   # no output means the port is free

“Operation not permitted”

The process belongs to another user. Use sudo kill <pid> only if you are sure what it is.

Pitfall: stale PIDs

PIDs are recycled. If you copy a PID, wait, then kill -9 it, you may hit an unrelated process. PortPeek re-checks the port owner and the process start time right before signalling, tries SIGTERM first, and only force-kills when you explicitly confirm — see how it works.