Can other people open localhost?
No. Their localhost points to their computer, not yours.
What is localhost:3000?
// works on your laptop. now let's make it work everywhere.
localhost is your computer, not the internet.
Open it and your browser talks back to your own machine.
127.0.0.1means “this computer.”- Nothing leaves your laptop.
- Only you can open it.
your computer
your browser
localhost = 127.0.0.1
localhost:3000 — famous on your laptop, invisible everywhere else.
:3000 is the app's door.
A port tells your computer which local app should answer.
- Vite, Next.js, Astro, and Express use ports such as
:3000or:5173. localhost:3000means “this computer, app at door 3000.”
your computer
one computer · many app doors
Quick answers
Does localhost need hosting?
Only when you want a public link. Hosting puts your files or app on an internet-connected server.
What's the quickest way to publish it?
Publish static files with a static host. If your project needs a server or database, choose an app host.
Can my local app or AI agent receive email?
Not directly: mail from the internet can't reach localhost. Give it an inbox it reads over an API instead, such as Revdoku, email addresses for AI agents and AI apps (made by the team behind this site). Or point Postmark or Mailgun inbound email at a tunnel such as ngrok.