How to Free Port 3000 on Mac, Linux & Windows

The Fastest Way: portrm

$ ptrm fix 3000

  Port 3000 in use
  Node.js (PID 12345) - React dev server
  SAFE - dev server, safe to kill

  Fix port 3000? [Y/n] Y
  Killed PID 12345
  Port 3000 is now free

Or without any prompts: ptrm fix 3000 -y

Install: npm install -g portrm | brew install abhishekayu/tap/portrm | npx portrm fix 3000

Check What is Using Port 3000

Before killing anything, see what is running:

$ ptrm 3000

  Port 3000
  Process:  node (PID 12345)
  Service:  React dev server (90% confidence)
  Memory:   14.2 MB
  Uptime:   2h 30m
  Safety:   SAFE - dev server

Free Port 3000 on macOS

# Find the process
$ lsof -i :3000
COMMAND  PID   USER  FD   TYPE DEVICE SIZE/OFF NODE NAME
node    12345  user  23u  IPv6 ...    0t0      TCP *:3000

# Kill it
$ kill -9 12345

# Or one-liner
$ kill -9 $(lsof -ti :3000)

Free Port 3000 on Linux

# Using lsof
$ lsof -ti :3000 | xargs kill -9

# Using fuser
$ fuser -k 3000/tcp

# Using ss
$ ss -tlnp | grep :3000
$ kill -9 <PID>

Free Port 3000 on Windows

# Find the process
> netstat -ano | findstr :3000
  TCP  0.0.0.0:3000  0.0.0.0:0  LISTENING  12345

# Kill it
> taskkill /PID 12345 /F

What Usually Uses Port 3000?

Use a Different Port Instead

If you do not want to kill the existing process, use another port:

$ PORT=3001 npm start              # React / Express
$ npx next dev --port 3001         # Next.js
$ npx vite --port 3001             # Vite

Prevent Port 3000 Conflicts

Use a .ptrm.toml config to assign dedicated ports to each service in your project:

$ ptrm init
# Creates .ptrm.toml with your services and ports

$ ptrm up
# Starts all services, auto-resolves conflicts

$ ptrm preflight 3000
# Check if port 3000 is free before starting