Node.js3 min read2026-03-01

Node.js Port Already in Use (Error: listen EADDRINUSE)

Fix Error: listen EADDRINUSE: address already in use :::3000 in Node.js and Express servers.

Error Code / Stack Trace

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

A Node.js or Express HTTP server fails to bind to the requested port because another process is already listening on that port.

A previous node server crashed or was stopped in the background without freeing the socket.
Another dev server (Next.js, React, or Docker) is running on port 3000.
nodemon spawned multiple orphan worker processes.

Locate the PID listening on the port.

bash

lsof -i :3000
# On Windows: netstat -ano | findstr :3000

Terminate the process by PID.

bash

kill -9 <PID>
# Or kill all node processes:
killall node
# Windows: taskkill /F /IM node.exe

Allow dynamic fallback port selection in Express.

javascript

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

Add graceful SIGINT / SIGTERM shutdown handlers to close server sockets cleanly.

Listen on port 0 (server.listen(0)), which instructs the OS to assign an unused ephemeral port.