Fix · Vercel and deploying

Build says "Module not found: Can't resolve"

What you may see

The build fails on an import that works on my computer
The file name has different capital letters than the import

Most likely cause

Linux (used by Vercel) treats Header.tsx and header.tsx as different files, or the package is missing from package.json, or the file was never saved to Git.

Check first (about two minutes)

Compare the import text with the real file name, letter by letter, including capitals.
Run git ls-files | grep -i <name> to see if Git has the file.

The fix prompt

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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 deploys websites on Vercel every day and explains it 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
Build says "Module not found: Can't resolve"

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
Linux (used by Vercel) treats Header.tsx and header.tsx as different files, or the package is missing from package.json, or the file was never saved to Git.

DO THESE STEPS, IN THIS ORDER
1. Find the import named in the error and the file it should point to.
2. Fix the capital letters in the import or the file name (with git mv, so Git sees the rename on every system).
3. If it is a package, check it is in package.json dependencies (not only installed locally) and add it with npm install <name>.
4. If the file is untracked, add and commit it. Then rebuild.
Stop and tell me if what you see does not match a step. Do not skip ahead.

CHECK THAT IT WORKED
- npm run build passes locally and the Vercel build passes.
Tell me exactly what I should see on the screen when it works.

DO NOT CHANGE
- Do not rename many files at once.
- 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

Find the import named in the error and the file it should point to.
Fix the capital letters in the import or the file name (with git mv, so Git sees the rename on every system).
If it is a package, check it is in package.json dependencies (not only installed locally) and add it with npm install <name>.
If the file is untracked, add and commit it. Then rebuild.

Do not do this

Do not delete the import to make the error go away.
Do not rename many files at once.

Try another entry