npm

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

Address Already in Use

The port your app is trying to bind to is already occupied by another process.

Common Causes

Previous instance of the app still running
Another app using the same port
Zombie process holding the port

Fixes

1. Find process using the port

lsof -i :3000   # macOS/Linux
netstat -ano | findstr :3000   # Windows

2. Kill the process
```
kill -9 <PID>
```
3. Use a different port
```
PORT=3001 npm start
```

Still not fixed?

• Search the exact error message on Stack Overflow or GitHub Issues
• Check the official docs for the language or tool
• Ensure your versions (Node, Python, npm, Docker) are up to date
• Try in a minimal reproduction (new project, single file)

Related Errors

Docker Port Already Allocated EACCES: Permission Denied

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All Errors

JavaScript Heap Out of Memory ModuleNotFoundError IndentationError Cannot Find Module Peer Dependency Warning CORS Policy Blocked TypeError: 'NoneType' Not Subscriptable Merge Conflict Docker Port Already Allocated ENOENT: No Such File or Directory KeyError MaxListenersExceededWarning RecursionError Detached HEAD State EACCES: Permission Denied ValueError No Space Left on Device ERR_REQUIRE_ESM FileNotFoundError