How to find what’s using a port on your Mac

The quick answer

Open Terminal and ask lsof which process is listening on the port:

lsof -nP -iTCP:3000 -sTCP:LISTEN

COMMAND   PID   USER   FD   TYPE  DEVICE SIZE/OFF NODE NAME
node    48211   you    23u  IPv6  0x...       0t0  TCP *:3000 (LISTEN)

• -iTCP:3000 limits it to TCP port 3000. Change the number for any other port.
• -sTCP:LISTEN shows only the server, not every connection to it.
• -n and -P skip DNS and port-name lookups, so it answers instantly and shows numbers.

To list every listening port on your Mac:

lsof -nP -iTCP -sTCP:LISTEN

“node” isn’t an answer: find which project it is

lsof tells you the command is node and the PID is 48211, but you probably have five Node projects. Two more commands get you the rest:

# The full command line: which script or framework
ps -o pid,ppid,etime,command -p 48211

# The working directory: which project folder
lsof -a -p 48211 -d cwd -Fn | tail -1

etime is how long it’s been running, and ppid is the parent process. Follow the parent (ps -o ppid,command -p <ppid>) and you’ll usually reach a shell, then the terminal, editor or AI agent that started it. If the parent is 1 (launchd), its terminal is gone: it’s an orphan, and nobody is going to stop it for you.

Check whether it’s exposed to your network

Look at the address in the NAME column:

Shows	Who can connect
127.0.0.1:3000 or [::1]:3000	Only this Mac
*:3000 or 0.0.0.0:3000	Anyone on the same network

Many dev servers bind to every interface by default, or when you pass --host. On shared Wi-Fi that means other people can load your app, its API, or an admin panel with no password. Bind to 127.0.0.1 unless you’re deliberately testing on your phone.

Then: stop it, or pick another port

If it’s a server you forgot about, stop it gracefully with its PID:

kill 48211

The full walkthrough, including stubborn processes and Docker, is in how to kill a process on a port.

If it’s something you need, start your new server on another port instead, for example PORT=3001 npm run dev or vite --port 5174.

Doing this without Terminal

Stat Space keeps this list in your menu bar. Every listening port shows its framework, project folder, the launcher behind it (Terminal, VS Code, Cursor, Claude Code, Docker, launchd) and its uptime. Anything bound to 0.0.0.0 gets a warning. From the row you can open it in the browser, copy the URL, show a QR code for your phone, or stop it.

From the terminal, the same answer is one command:

statspace port 3000