Fix · Node, npm and build

localhost refused to connect (ERR_CONNECTION_REFUSED)

What you may see

The browser cannot open localhost:3000
The terminal looks fine

Most likely cause

The dev server is not running, runs on another port, or only listens on a different address.

Check first (about two minutes)

Look at the terminal: does it say Ready and print an address? Use exactly that address.
Is the terminal still running or did it stop with an error?

The fix prompt

What you type here never leaves your browser. The search runs on this page, and nothing is sent to a server or to an AI.

The exact error or what you see

What you did before it happened

Kept only in this browser, on this device. Keys and passwords are removed before anything is saved.

Prompt language

You are a patient senior engineer who knows Node.js, npm and build tools and explains them to people who are not developers. I am not a developer, so explain every step in plain words and tell me exactly which button, menu or command you mean. If you are not sure about something, say so; do not guess.

THE PROBLEM
localhost refused to connect (ERR_CONNECTION_REFUSED)

THE EXACT ERROR OR WHAT I SEE
[paste the exact error here]

WHAT I DID BEFORE IT HAPPENED
[write in a few words what you did before it happened]

MOST LIKELY CAUSE
The dev server is not running, runs on another port, or only listens on a different address.

DO THESE STEPS, IN THIS ORDER
1. Check whether the dev server is running and which address and port it prints.
2. Try localhost and 127.0.0.1 and the printed port; if a phone must reach it, explain the local network address and the host option.
3. If it stopped, read the last error and fix it.
Stop and tell me if what you see does not match a step. Do not skip ahead.

CHECK THAT IT WORKED
- The browser shows the app at the printed address.
Tell me exactly what I should see on the screen when it works.

DO NOT CHANGE
- Do not open firewall ports to the internet.
- Anything I did not ask about: the design, the text, other pages, other settings or the data.
- Do not delete files, data or branches, do not reset or force-push, and do not rewrite history, unless you first show me exactly what would be lost and I say yes.
- Do not paste, print or ask me to paste a password or secret key into this chat. If one is needed, tell me which settings page of the right service to store it in.

WHEN YOU FINISH
Explain in simple words what you changed (file by file or setting by setting), why you changed it, and how I can undo it.

Paste it into Claude, ChatGPT, Gemini or Cursor, then follow what it says.

After you tried it, did it work?

Steps

Check whether the dev server is running and which address and port it prints.
Try localhost and 127.0.0.1 and the printed port; if a phone must reach it, explain the local network address and the host option.
If it stopped, read the last error and fix it.

Do not do this

Do not share a localhost link with customers; deploy a preview instead.
Do not open firewall ports to the internet.

Try another entry