Supabase auth problems usually come from configuration, not code bugs: Site URL and redirect URLs that don't match your deployed domain, email confirmation or email sending limits blocking sign-ups, server-rendered apps that don't store sessions in cookies, OAuth providers missing the correct callback URL, or Row Level Security that's enabled without the policies users need. RLS issues are especially confusing because queries often return an empty result instead of an error.

Signs Your Supabase Auth Is Misconfigured

• Login or OAuth redirects to localhost after deployment

• Users see Email not confirmed or never receive confirmation emails

• Users are logged out after refreshing the page

• The user is logged in on the client, but server pages treat them as logged out

• Queries return an empty array once Row Level Security is enabled

• Google or GitHub login fails with a redirect or callback error

• Password reset or magic links open the wrong page or expire

Why Supabase Auth Breaks

1. Site URL and redirect URLs

Supabase only redirects users to URLs allowed in your project's authentication URL settings. If the Site URL is still localhost or your production and preview domains aren't listed as redirect URLs, sign-in, magic links, and password resets send users to the wrong place.

2. Email confirmation and sending limits

When email confirmation is enabled, users can't sign in until they confirm. Supabase's built-in email service is intended for development and has tight sending limits, so production apps without a custom SMTP provider often stop sending confirmation and reset emails.

3. Sessions in server-rendered apps

In frameworks like Next.js, the server can't read a session stored only in the browser. Server-rendered apps need Supabase's server-side helpers to store sessions in cookies and refresh them, typically through middleware. Without that, users appear logged in on the client and logged out on the server.

4. OAuth provider setup

For Google, GitHub, and other providers, the provider's console must include Supabase's callback URL, and your app must handle the returned code correctly. A missing callback URL or skipped code exchange ends the login with an error or a user who isn't signed in.

5. Row Level Security without the right policies

Enabling RLS denies all access until policies allow it. Missing or incorrect policies make queries return no rows, often without an error. The opposite risk is just as serious: tables without RLS, or policies that are too permissive, can expose one user's data to others.

How We Diagnose the Auth Problem

1. Review authentication settings. Check Site URL, redirect URLs, providers, and email confirmation settings against your real domains.

2. Trace the login flow. Follow sign-up, sign-in, callback, and redirect in the browser and server logs.

3. Check session handling. Confirm how sessions are stored and refreshed on both client and server.

4. Test email delivery. Verify whether confirmation and reset emails are sent, delayed, or rate limited.

5. Audit Row Level Security. Review every table's RLS status and policies, and test queries as real signed-in users.

6. Check key usage. Confirm the service role key is never exposed in client code.

How We Fix It

We test every auth flow, including sign-up, login, logout, OAuth, and password reset, on your deployed domain.

Example Fix

Situation: A Next.js marketplace on Supabase worked in development, but after launch users were logged out on every page load and saw empty dashboards.

Cause: Sessions were stored only in the browser, so server-rendered pages never saw the user. Once that was fixed, dashboards were still empty because RLS was enabled on the listings table with no select policy for owners.

Fix: Implemented cookie-based sessions with middleware refresh, added owner-based RLS policies for listings and orders, updated redirect URLs for production, and configured custom SMTP for confirmation emails.

Result: Users stayed signed in across pages, dashboards showed each seller's own data only, and confirmation emails arrived reliably.

How to Keep It From Happening Again

• Test auth on a preview deployment before every release, not only on localhost.

• Write RLS policies with tests that query as different users and confirm who can see what.

• Use a custom SMTP provider before launch so auth emails don't stop under real sign-up volume.

What You Get

• Root cause confirmed and explained

• Working sign-up, login, OAuth, and password reset flows

• Tested Row Level Security policies for affected tables

• Short security notes on keys and data access

Frequently Asked Questions

Why does Supabase login redirect to localhost? The project's Site URL or redirect URL settings still point to localhost, or your production domain isn't in the allowed redirect list. Update both to match the deployed domain.

Why does my Supabase query return an empty array? Row Level Security is likely enabled without a policy that allows the signed-in user to read those rows. Supabase returns no data rather than an error in that case.

Why do users get logged out on refresh in Next.js? The session isn't being stored in cookies and refreshed for server rendering. Server-rendered apps need Supabase's server-side auth setup and middleware.

Why aren't Supabase confirmation emails arriving? The built-in email service has strict sending limits intended for development. Production apps should use a custom SMTP provider.

Is my Supabase data safe if RLS is disabled? No. Tables exposed through the API without RLS can be read or changed by anyone with your public key. Enable RLS and add policies for every exposed table.

Related Problems

• Google OAuth login not working

• Lovable app not deploying

• AI-built app you can't ship

• Stripe webhook not working

• CORS error blocking API requests

Get Your Users Signed In

Share the auth error or the flow that's failing. Get a diagnosis and a fixed price.

Get Help Now