OAuth Error: redirect_uri_mismatch

OAuth clients must register every redirect URI exactly—including scheme, host, port, path, and trailing slash. SPA libraries that default to http://localhost:3000/ will fail if the console only lists http://localhost:3000/callback.

Update the provider dashboard, redeploy, and clear stale state parameters. Mobile custom URL schemes need their own registered entries. OAuthFixer maps errors to the fields you must edit.