EADDRINUSEaddress already in use :::3000
Port 3000 is taken again.
Kill it from your menu bar.
Port Monitor lists every process on your dev ports with the command, PID and project folder it came from. One click stops it. No lsof, no Activity Monitor, no guessing.
Pay once, keep it forever. Or try it free for 7 days.
This one is live. Click × to kill something. Nothing real will die.
You know the drill.
A dev server from yesterday, a preview from another branch, an agent that never shut down. Something is holding the port, and finding it takes longer than the fix.
Without Port Monitor
$ npm run dev
Error: listen EADDRINUSE: address already in use :::3000
$ lsof -i :3000
COMMAND PID USER FD TYPE NODE NAME
node 46999 mikko 23u IPv6 TCP *:3000 (LISTEN)
$ kill 46999
$ npm run dev
Error: listen EADDRINUSE: address already in use :::3000
$ kill -9 46999
$ npm run devFour commands, one PID typed by hand, and still no idea which project it was.
With Port Monitor
node
~/code/yesterdays-experiment/web
- 1Click the icon in your menu bar. It already shows how many ports are busy.
- 2Find the row. Port, command and the folder it was started from.
- 3Click ×. Port Monitor sends SIGTERM, then SIGKILL if the process ignores it.
Kill All does the same for every listed process, and the list refreshes itself a few seconds later.
How it works
Three steps, and the third one is the only one you will repeat.
- 01
Install it once
Download the app, drag it to Applications, open it. It lives in your menu bar, starts with your Mac if you want, and updates itself. The first 7 days are free with no account.
- 02
Glance at the count
The menu bar icon shows how many of your dev ports are in use right now. Zero means you are clear. Anything else, click it.
- 03
Stop what you don't need
Each row shows the port, the command, its PID and the project folder. Click × to stop one, or Kill All (⌘⇧K) to clear the list before you start fresh.
Not sure yet? Try it free for 7 days.
The trial is the whole app. No account, no card. After 7 days it keeps listing your ports, and killing waits until you paste in a license key.
macOS 26 (Tahoe) or later. Apple silicon and Intel.
Built for the way you actually work
A utility should be obvious in the first ten seconds and stay out of the way after that.
See where it came from
Every row shows the working directory the process was started in, so you know which project left it running.
Catches what agents leave behind
Claude Code, Cursor, Codex and friends start dev servers and preview builds all day. They show up here like everything else.
System services stay hidden
AirPlay, Control Center, Spotify and other macOS services are excluded out of the box, so you only see your own work. Add your own exclusions in Settings.
Your range, not ours
3000 to 9999 by default. Watch a single port, a list or several ranges. Applies instantly.
Fresh without draining your battery
Scans every 4 seconds while ports are busy and slows down when everything is idle. Refresh on demand with ⌘R.
Keyboard first
⌘R refresh, ⌘⇧K kill all, ⌘, settings, ⌘Q quit. Nothing to learn.
Nothing leaves your Mac
Port and process data is read locally with lsof and ps and never uploaded. The app only talks to our server to check your trial or license.
Native, small, dark mode
Written in Swift and SwiftUI. No Electron, no dock icon, follows your system appearance.
One price. Pay once.
Less than a coffee, and it will save you more than one. Buy a license, paste it into Settings, and it is yours for good.
- Lifetime license, every future update included
- Use it on all Macs you own
- Kill single processes or everything at once
- Configurable port range and exclusions
- Launch at login, automatic updates
Port Monitor license
4,99 €one-time
Shown in your local currency at checkout. VAT included where it applies.
Secure payment by Stripe. License key arrives by email within a minute.
By buying you accept the terms of sale. 14-day refund, no questions asked.
No account, no card. The full app.
Questions
Anything else? hello@port-monitor.app
Replies usually within a day.
Which ports does it watch?
3000 to 9999 by default, which covers most dev servers, preview builds and local services. You can change it to any single ports, lists or ranges in Settings, and exclude ports you never want to see.
How does killing work?
Click the × on a row. Port Monitor sends the process a SIGTERM so it can shut down cleanly, waits a moment, and only sends SIGKILL if it is still running. Kill All does the same for every listed process.
Does it need admin rights?
No. It runs as your user and can stop any process you own, which is every dev server and tool you started. Processes owned by root or the system are shown but can't be killed, and you will see a clear message if you try.
Could I kill something important by accident?
Only processes listening on the ports you chose are listed, and common macOS services such as AirPlay, Control Center, Spotify and Discord are excluded by default. Each row shows the command and folder so you know what you are stopping.
What happens after the free trial?
After 7 days the app keeps listing your ports, but killing is disabled until you enter a license key. Buy one on this page, paste it into Settings and everything is unlocked on all your Macs.
What does the app send to your server?
Only what is needed for the trial and license: an anonymous hardware identifier to keep track of the trial, and your license key when you activate it. Port and process information never leaves your Mac. Updates are checked through Sparkle without any system profiling.
Which macOS versions are supported?
macOS 26 (Tahoe) or later on Apple silicon and Intel Macs. The app uses the current SwiftUI features, which is why older versions are not supported.
What if it does not work for me?
Try the free trial first, it is the full app. If you bought a license and something is wrong, email hello@port-monitor.app and we will fix it or sort out a refund.
Port 3000 will be taken again tomorrow.
Next time it takes one click. 4,99 € once, for every Mac you own, forever.