Default dev server ports: 3000, 5173, 8000, 8080 and more

By techynAR · Updated 23 October 2026

Short answerMost Node frameworks default to port 3000 (Next.js, Create React App, Express examples), Vite uses 5173, Angular 4200, Astro 4321, Django 8000, Flask 5000 and Rails 3000. Many of them collide on 3000, which is the most common cause of “address already in use”.

Web frameworks

• 3000: Next.js, Create React App, Remix, Rails, most Express tutorials
• 5173: Vite (and SvelteKit, which uses Vite)
• 4200: Angular (ng serve)
• 4321: Astro
• 8000: Django (runserver), FastAPI/uvicorn examples, python -m http.server uses 8000
• 5000: Flask (taken by AirPlay Receiver on newer macOS)
• 8080: webpack-dev-server, many Java servers, a common fallback
• 4000: Phoenix, Jekyll
• 1313: Hugo
• 8888: Jupyter

Databases and services

• 5432: PostgreSQL
• 3306: MySQL and MariaDB
• 6379: Redis
• 27017: MongoDB
• 9200: Elasticsearch
• 5672 and 15672: RabbitMQ and its management page

Why collisions happen

Two projects that both default to 3000 can't run at once, and the second one fails. Some tools (Vite, and Next.js when you haven't set a port) pick the next free port by themselves; others stop with an error. When you run several projects at once, give each its own port.

See what's actually running

The defaults tell you what a server probably is, not what is actually listening. Portmole reads each listening process's command and project folder, so :3000 shows up as “my-app (Next.js)” instead of a bare number.