Port Manager
See every listening port and the process that owns it — and free up port 3000.
"Port 3000 is already in use." By what? Port Manager answers instantly: every TCP port your Mac is listening on, with the owning process and PID, refreshed live.
Read the list
Open Port Manager. Each row is one listening port:
- Port — dev-server ports (3000–5999, 8000–9000, 9229) are tinted so they stand out from system noise
- Process and PID — who owns it
- The list refreshes every 2 seconds while you're looking at it
Search filters by port number, process name, or PID. The dev-ports filter hides system daemons entirely.
Open in browser
A localhost web server on the port? Click the link icon and it opens http://localhost:PORT in your browser.
Kill a process
Found the zombie dev server holding your port:
- Click Copy kill on its row.
- Paste into Terminal (⌘V) and press ⏎ — it's a ready-made
kill -9 <pid>command. - The row disappears on the next refresh. Port free.
Why doesn't the button just kill it directly?
The App Store version of Developers Kit runs in the macOS sandbox, and the sandbox forbids apps from terminating other processes — that's a real security boundary, not a design choice. Copying the exact command is the honest workaround: you run it, with your authority, in Terminal.
The direct-download (Developer ID) build of the app is not sandboxed and shows a real Kill button instead.