Fix · Node, npm and build

Unexpected token '<' in JSON (I got a web page instead of data)

What you may see

fetch or JSON.parse fails with Unexpected token <
It says "is not valid JSON"

Most likely cause

The address answered with an HTML page (often an error or a login page) instead of JSON, or with nothing at all.

Check first (about two minutes)

Open the same address in a browser tab: do you see JSON or a web page?
In the network tab, read the status code of that request.

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
Unexpected token '<' in JSON (I got a web page instead of data)

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 address answered with an HTML page (often an error or a login page) instead of JSON, or with nothing at all.

DO THESE STEPS, IN THIS ORDER
1. Show the fetch call and its address. Check the address is right (a missing /api, a wrong domain, http versus https).
2. Read the real status and body first (response.status and response.text()) before parsing.
3. Fix the cause (wrong address, a 404, a redirect to login, a crash in the route) and add a clear error message for non-200 answers.
Stop and tell me if what you see does not match a step. Do not skip ahead.

CHECK THAT IT WORKED
- The address returns JSON with status 200, and the page shows its data.
Tell me exactly what I should see on the screen when it works.

DO NOT CHANGE
- Do not wrap the parse in an empty try/catch.
- 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

Show the fetch call and its address. Check the address is right (a missing /api, a wrong domain, http versus https).
Read the real status and body first (response.status and response.text()) before parsing.
Fix the cause (wrong address, a 404, a redirect to login, a crash in the route) and add a clear error message for non-200 answers.

Do not do this

Do not guess: read the body of the response.
Do not wrap the parse in an empty try/catch.

Try another entry