Fixing Google Auth 403 in Lovable + Supabase

The Problem

You've set up Google OAuth in your Lovable project with Supabase, but users get a 403 error when trying to sign in. The error message doesn't tell you much.

This happens whether you're using Lovable Cloud or your own Supabase project — the Google Cloud Console settings are usually the culprit.

Common Causes

1. Redirect URI mismatch — Google is strict about exact URLs
2. OAuth Consent Screen incomplete — missing required fields
3. App in Testing mode — users not added as testers
4. Wrong credentials — copy-paste errors happen

Solution

1. Check Redirect URIs (Most Common Issue)

Go to Google Cloud Console > APIs & Services > Credentials > Your OAuth Client.

For Supabase (your own project):

https://[PROJECT_REF].supabase.co/auth/v1/callback

For Lovable Cloud:

https://[YOUR-PROJECT].lovable.cloud/auth/v1/callback

⚠️ Important: Add the full redirect URI, not just the JavaScript origin. This is where 90% of 403 errors come from.

2. Complete OAuth Consent Screen

Go to OAuth Consent Screen and verify:

• App name and logo are set
• User support email is filled
• Scopes include email and profile
• Developer contact info is complete

3. Add Test Users

If your app is in "Testing" mode (not published to production):

• Go to OAuth Consent Screen > Test users
• Add every email that needs to sign in
• Users not on this list will get 403

💡 Tip: Even your own email needs to be on the test users list if you're in Testing mode. This catches a lot of people.

4. Verify Credentials in Both Places

Double-check that Client ID and Client Secret match exactly between:

• Google Cloud Console
• Supabase Dashboard (or Lovable settings)

Quick Checklist

• Redirect URI is exact (includes /auth/v1/callback)
• OAuth Consent Screen is 100% complete
• Test users added (if in Testing mode)
• Credentials match in both places

Still Stuck?

ℹ️ Note: Check Google Cloud Console > APIs & Services > Credentials > View usage. It shows recent errors and can help pinpoint the issue.