Fix · Node, npm and build

Error occurred prerendering page during next build

What you may see

The build fails on one page with a prerender message
It says window is not defined or cannot read properties of undefined

Most likely cause

While building, the page code runs on a server without a browser, and it uses browser-only things (window, localStorage) or data that is empty at build time.

Check first (about two minutes)

Read which page is named in the 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
Error occurred prerendering page during next build

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
While building, the page code runs on a server without a browser, and it uses browser-only things (window, localStorage) or data that is empty at build time.

DO THESE STEPS, IN THIS ORDER
1. Open that page and find the line that uses window, document, localStorage, or data that may be missing.
2. Move browser-only code into an effect that runs after the page loads, or into a client-only component.
3. Handle missing data with a safe default or an empty state.
Stop and tell me if what you see does not match a step. Do not skip ahead.

CHECK THAT IT WORKED
- npm run build completes and the page opens.
Tell me exactly what I should see on the screen when it works.

DO NOT CHANGE
- Do not wrap the whole site in client-only mode to avoid the error.
- 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

Open that page and find the line that uses window, document, localStorage, or data that may be missing.
Move browser-only code into an effect that runs after the page loads, or into a client-only component.
Handle missing data with a safe default or an empty state.

Do not do this

Do not set fake data to pass the build.
Do not wrap the whole site in client-only mode to avoid the error.

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