Error 400: redirect_uri_mismatch (Sign in with Google)

What it means in plain English

Google only sends users back to addresses you've pre-approved. The address your app asked for isn't on that list, letter-for-letter.

Likely causes

• The Supabase callback URL (https://<project-ref>.supabase.co/auth/v1/callback) isn't in Google's Authorized redirect URIs.
• Mismatch in http vs https, www, capital letters or a trailing slash; Google requires an exact match.
• You're using a custom auth domain or a different OAuth client ID in production.

How to fix it, step by step

1. Supabase → Authentication → Providers → Google: copy the Callback URL shown there.
2. Google Cloud Console → Google Auth Platform → Clients → your Web client.
3. Under Authorized redirect URIs, paste the Supabase callback URL exactly. Under Authorized JavaScript origins, add your site, e.g. https://yourapp.com.
4. Save (Google changes can take a few minutes).
5. Make sure the Client ID and Secret in Supabase match this same Google client.
6. After Google, Supabase sends users to your app; that must also be allowed (see the localhost redirect page).

How to check it worked

• Click 'Sign in with Google' on the live site; you should reach the consent screen and return signed in.
• No 400 error page.

Sources

• https://developers.google.com/identity/protocols/oauth2/web-server (opens in a new tab)
• https://supabase.com/docs/guides/auth/social-login/auth-google (opens in a new tab)
• https://supabase.com/docs/guides/auth/redirect-urls (opens in a new tab)