Fix · Supabase and databases

"User already registered" when signing up

Not checked against the vendor's current screens

What you may see

A new sign-up says the user already exists
The person says they never signed up

Most likely cause

An account with this email exists, maybe created through Google or by an earlier test.

Check first (about two minutes)

Search the Users list in the dashboard for this email.

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 careful senior engineer who knows Supabase (database, login and file storage) 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.

Menu and button names change over time. If you cannot find a button or page I mention, say so and tell me what to look for instead of guessing.

THE PROBLEM
"User already registered" when signing up

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
An account with this email exists, maybe created through Google or by an earlier test.

DO THESE STEPS, IN THIS ORDER
1. Show how the app signs in versus signs up and what happens when the email exists.
2. Offer "sign in" and "forgot password" paths on that message.
3. Do not reveal to strangers whether an email exists, if the project is public-facing.
Stop and tell me if what you see does not match a step. Do not skip ahead.

CHECK THAT IT WORKED
- An existing user can reach sign-in from the message and a new email signs up.
Tell me exactly what I should see on the screen when it works.

DO NOT CHANGE
- Do not delete users to make a sign-up pass.
- 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 how the app signs in versus signs up and what happens when the email exists.
Offer "sign in" and "forgot password" paths on that message.
Do not reveal to strangers whether an email exists, if the project is public-facing.

Do not do this

Do not merge accounts by email alone without confirming ownership.
Do not delete users to make a sign-up pass.

Fix it Sign-up says the email is already used (but I never signed up)

Try another entry