Localhost

Localhost is your private development playground. Every change you make appears here instantly, letting you build and test before anyone else sees your work.

How Localhost Works

1. You start a development server (usually with npm run dev)
2. Your computer begins hosting your app locally
3. You visit localhost:3000 in your browser
4. Your app appears — running entirely on your machine

No internet connection needed. No hosting costs. Just you and your code.

What's the :3000?

The number after the colon is the port — think of it as a door number on your computer. Different apps use different ports:

Common Localhost Issues

• "Port already in use" — Another app is using that port. Stop it or use a different port
• "Cannot connect" — Your dev server isn't running. Check the terminal
• Changes not showing — Try hard-refreshing with Cmd+Shift+R or Ctrl+Shift+R

From Localhost to the Internet

Localhost is step one. When your app works locally, you deploy it to make it accessible to everyone. Services like Vercel and Netlify handle this — taking your local project and putting it on the web.