Fix: Port 3000 Is Already in Use (EADDRINUSE)

The Error

You start your development server and get one of these errors:

Node.js / Express:

Error: listen EADDRINUSE: address already in use :::3000

React (create-react-app):

Something is already running on port 3000.

Next.js:

Port 3000 is already in use.
Use `next dev --port` to specify a different port.

All of these mean the same thing: something else on your machine is already listening on port 3000.

Why This Happens

Port 3000 can only be used by one process at a time. Common causes:

• A previous dev server is still running. You closed the terminal tab but the process didn’t stop.
• Another project is using the same port. You have two apps both defaulting to port 3000.
• A zombie Node.js process. The process crashed but didn’t release the port.
• A Docker container is mapping a container port to 3000 on your host machine.
• A system or background service (like a database admin panel) is bound to that port.

Fix 1: Find and Kill the Process (macOS / Linux)

Find which process is using port 3000:

lsof -i :3000

You’ll see output like:

COMMAND   PID   USER   FD   TYPE  DEVICE SIZE/OFF NODE NAME
node    12345   you   23u  IPv6  0x1234      0t0  TCP *:3000 (LISTEN)

Kill the process using its PID. First try a graceful shutdown:

kill 12345

If the process doesn’t stop after a few seconds, force-kill it:

kill -9 12345

One-liner — find and kill in a single command:

lsof -ti :3000 | xargs kill

The -t flag makes lsof output only the PID, which is piped directly to kill. Use xargs kill -9 instead if the graceful kill doesn’t work.

Fix 2: Find and Kill the Process (Windows)

Find which process is using port 3000:

netstat -ano | findstr :3000

You’ll see output like:

  TCP    0.0.0.0:3000    0.0.0.0:0    LISTENING    12345

The last number (12345) is the PID. Kill it:

taskkill /PID 12345 /F

One-liner using PowerShell:

Stop-Process -Id (Get-NetTCPConnection -LocalPort 3000).OwningProcess -Force

Fix 3: Use npx kill-port (Cross-Platform)

The simplest solution that works on macOS, Linux, and Windows:

npx kill-port 3000

You can kill multiple ports at once:

npx kill-port 3000 3001 8080

No global install required — npx downloads and runs it on the fly.

Fix 4: Change the Default Port

If you’d rather keep whatever is on port 3000 running, change your app’s port instead.

React (create-react-app):

PORT=3001 react-scripts start

On Windows (cmd):

set PORT=3001 && react-scripts start

Or use cross-env for a cross-platform solution in package.json:

{
  "scripts": {
    "start": "cross-env PORT=3001 react-scripts start"
  }
}

Next.js:

npx next dev --port 3001

Or in package.json:

{
  "scripts": {
    "dev": "next dev --port 3001"
  }
}

Express:

Change the port in your code:

const port = process.env.PORT || 3001;
app.listen(port, () => {
  console.log(`Server running on port ${port}`);
});

Then either edit the fallback value or set the environment variable:

PORT=3001 node server.js

Vite:

npx vite --port 3001

Or in vite.config.js:

export default defineConfig({
  server: {
    port: 3001,
  },
});

Still Not Working?

Multiple Node Processes Are Running

Sometimes several zombie Node processes pile up. Kill them all at once:

macOS / Linux:

killall node

Windows (cmd):

taskkill /IM node.exe /F

Warning: This kills every Node.js process on your machine, including unrelated ones.

A Docker Container Is Using the Port

Check if a Docker container has port 3000 mapped:

docker ps --format "table {{.Names}}\t{{.Ports}}" | grep 3000

If you find one, stop it:

docker stop <container_name>

Or remove the port mapping by changing -p 3000:3000 to a different host port (e.g. -p 3001:3000) when you run the container.

A System Process Is Using the Port

If lsof or netstat shows a system process (not Node) on port 3000, don’t kill it blindly. Check what it is first:

macOS / Linux:

lsof -i :3000

Look at the COMMAND column. If it’s something like Grafana, a database admin panel, or another known service, either disable that service or change your app’s port instead (see Fix 4).

On macOS, AirPlay Receiver is known to occupy port 5000 (not 3000), but it’s worth checking if any macOS system service is using your port. You can disable AirPlay Receiver under System Settings > General > AirDrop & Handoff > AirPlay Receiver if it conflicts with other projects.

The Port Is Freed but the Error Persists

After killing the process, if you still get the error, wait a few seconds. The OS may keep the port in a TIME_WAIT state briefly. If it persists:

macOS / Linux — check if anything is still holding it:

lsof -i :3000

If the output is empty and the error continues, restart your terminal or IDE. Some tools cache the port assignment.

Related: If you’re seeing npm dependency errors when setting up your project, see Fix: npm ERR! ERESOLVE unable to resolve dependency tree.