Supabase Auth errorSupabase Auth: bad_oauth_state

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Why Supabase rejects the state, and the fix

1. 01

   The sign-in took too long

   Each OAuth state expires; the Auth server never sets the limit below five minutes. A user who stops at the provider’s login or 2FA screen comes back to “OAuth state has expired”. Catch the error and restart sign-in.

   const params = new URLSearchParams(window.location.search);
   if (params.get('error_code') === 'bad_oauth_state') {
     showRetry(() => supabase.auth.signInWithOAuth({
       provider: 'google',
       options: { redirectTo: `${location.origin}/auth/callback` },
     }));
   }

2. 02

   The app made its own state

   “OAuth state (data echoed back by the OAuth provider to Supabase Auth) is not in the correct format.” Supabase docs, Auth error codes (bad_oauth_state)

   Custom OAuth code that sends the user to Google with its own state value fails, because Supabase only accepts the state ID it created. Let signInWithOAuth build the provider URL.

3. 03

   The callback belongs to another project

   A staging and a production project share one OAuth client, and the provider sends users to the wrong callback. That project has no record of the state, so it returns “not found or expired”. Use one OAuth client per project, or list each callback URL exactly.

4. 04

   The error lands on the Site URL

   Also check: when the state fails, Supabase can’t read the redirectTo address saved with it, so users land on the Site URL, or the external redirect URL if one is set. Read the error there too. A missing state returns bad_oauth_callback, and a reused PKCE state returns flow_state_already_used.

Checked against the vendor’s docs on November 9, 2026: Supabase docs: Auth error codes; Supabase Auth source: external.go (state checks); Supabase Auth source: configuration.go (flow state expiry); Supabase docs: PKCE flow.

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Related: Supabase invalid flow state (code verifier) · Supabase OAuth provider disabled · Google OAuth redirect_uri_mismatch · Supabase PGRST200