The problem
Developers running multiple local services — API servers, databases, webpack dev servers — frequently need to know what is listening on which port, but running lsof -iTCP -sTCP:LISTEN or netstat -an produces walls of unformatted text that are slow to read and impossible to scan at a glance.
If you've hit this before, you know how it goes — you cycle through terminal tabs running lsof -iTCP -sTCP:LISTEN -n -P, squinting at the output, trying to find the process on port 3000.
As a solution, I created portmap
Scan all listening ports on localhost and visualise them in a browser dashboard with process names and PIDs
Zero-dependency Node.js, so you can run it immediately:
npx portmap
Output in terminal:
portmap dashboard → http://127.0.0.1:7777
Press Enter to stop.
The browser opens a live dashboard:
| Port | Process | PID | Address |
|---|---|---|---|
| 3000 | node | 14321 | *:3000 |
| 5432 | postgres | 1892 | 127.0.0.1:5432 |
| 6379 | redis-ser | 2104 | 127.0.0.1:6379 |
| 8080 | python3 | 19834 | *:8080 |
Hit Refresh to rescan. Press Enter in the terminal to stop. Auto-closes after 60s.
How it works
Uses Node.js child_process.execSync to run lsof -iTCP -sTCP:LISTEN -n -P (macOS/Linux) or netstat -ano (Windows), parses port/PID/process-name triples with regex, then serves a self-contained HTML dashboard via the built-in http module and opens the browser automatically.
Why I built it
Found the complaint repeatedly on r/webdev and r/node — developers juggling Postgres, Redis, a webpack server, and a Node API all at once constantly type lsof or netstat and squint at the output. No popular zero-dep Node.js tool presents this data visually. A local web dashboard is a natural fit: the output is tabular, colour and typography help enormously, and auto-closing keeps it lightweight.
Try it
npx portmap --help
Part of µ micro — one new developer tool, shipped every day. All tools are zero-dependency Node.js and run instantly with npx.
