Kill the process on port 3000 on a Mac

Your dev server fails with EADDRINUSE or picks port 3001 because something already has 3000. Find it with lsof, then stop it with kill.

Find what's on the port

lsof -nP -iTCP:3000 -sTCP:LISTEN

COMMAND   PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
node    48213 you    23u  IPv6 0x1f…      0t0  TCP *:3000 (LISTEN)

-iTCP:3000 picks the port, -sTCP:LISTEN shows only the server and not the browser tabs connected to it, and -nP skips name lookups so it answers instantly. The number under PID is what you stop.

Stop it

kill 48213

kill sends SIGTERM, which lets the server close its connections and exit cleanly. If it's still listed a few seconds later, force it with kill -9 48213.

Or find and stop it in one line. -t makes lsof print only the PID:

kill $(lsof -t -iTCP:3000 -sTCP:LISTEN)

When it comes straight back

• A watcher restarted it. nodemon, pm2, turbo or a concurrently script start the server again when it dies. Find the parent with ps -o pid,ppid,command -p 48213, then stop that, or press Ctrl-C in the terminal that runs it. For pm2: pm2 stop all.
• A container has it. If the COMMAND column shows Docker's or OrbStack's own process instead of node or python, a container published the port. Find it with docker ps --filter publish=3000 and stop it with docker stop <name>.
• lsof shows nothing, but the port is still taken. It belongs to another user or root. Run the same command with sudo to see it.