WhatThePort

How to see every dev server running on your Mac

List every localhost server and listening port on macOS from the terminal, work out which project each one belongs to, and keep them in view from the menu bar.

· 3 min read

Open localhost:3000, 3001, 5173, 8000 in turn and you’ll find out what’s running, one guess at a time. Here’s how to see all of it at once.

List every listening port

lsof -nP -iTCP -sTCP:LISTEN

This prints every process on your Mac that’s waiting for TCP connections. Each row has the command, the PID, and the address in the NAME column: *:3000 means any address on port 3000, and 127.0.0.1:5432 means only local connections on port 5432.

The list includes a lot that isn’t yours: ControlCenter, rapportd, Spotify, Dropbox. To see only likely dev servers:

lsof -nP -iTCP -sTCP:LISTEN | grep -iE '^(node|bun|deno|python|ruby|java|go|php)'

Turn PIDs into projects

A list of node processes isn’t much help when you have six. This loop prints the port, PID and folder of each one:

for pid in $(lsof -t -a -iTCP -sTCP:LISTEN -c node -c bun -c '/^python/i' -c ruby); do
  port=$(lsof -nP -a -p "$pid" -iTCP -sTCP:LISTEN -Fn | grep -m1 '^n' | sed 's/.*://')
  dir=$(lsof -a -p "$pid" -d cwd -Fn | grep '^n' | cut -c2-)
  echo "$port  $pid  $dir"
done | sort -n

3000  48213  /Users/tom/code/marketing-site
5173  51002  /Users/tom/code/editor
6006  51190  /Users/tom/code/design-system
8000  39921  /Users/tom/code/api/.worktrees/fix-auth

From the folder you can get the git branch (git -C <dir> branch --show-current) and the project name from its package.json.

Check memory and CPU

Activity Monitor shows memory per process, but a dev server is usually several processes: npm, the framework’s CLI, a server worker, a TypeScript checker, maybe a bundler. To see the whole tree:

pgrep -P 48213   # direct children
ps -o pid,ppid,rss,%cpu,command -g $(ps -o pgid= -p 48213)

Add up the rss column (in kilobytes) for a rough total. Next.js and Storybook servers can easily reach 1–3 GB once you’ve clicked around for a while. There’s more on that in Dev servers eating your RAM.

Why not netstat?

netstat -an | grep LISTEN shows listening ports but not, by default, which process owns them. lsof gives you the PID and command in one step, so it’s the better starting point on macOS.

Or keep them in the menu bar

The commands above answer the question once. If you run more than a couple of servers, or let coding agents start them for you, you’ll want the answer all the time.

WhatThePort is a free, open-source menu bar app that does exactly what the loop above does, every two seconds: it reads listening sockets with lsof, then inspects each process tree for its folder, command, memory and CPU. For each server it shows:

  • the port, with a stable color so :3000 always looks the same
  • the project name from package.json, pyproject.toml, Cargo.toml, go.mod or Gemfile, and the framework
  • the git branch, and whether its worktree has been deleted
  • uptime, memory and CPU for the whole process tree, with ten minutes of history
  • the Claude Code, Codex or Conductor session that started it, if any

Press ⌥⌘P to open it, click a server to open it in the browser, or stop it. Prefer the terminal? wtp shows the same list there, and wtp list --json prints it for scripts.

Download WhatThePort for Apple Silicon Macs on macOS 14 or later, or try the interactive demo.