Troubleshooting Sign in with Vercel

When users try to authorize your app, several errors can occur. Common troubleshooting steps include:

• Checking that all required parameters are included in your requests
• Verifying your app configuration in the dashboard
• Reviewing the Authorization Server API documentation
• Checking the Getting Started guide for implementation examples

Vercel handles authorization errors in two ways:

• Error page: Shown when critical parameters are missing or invalid
• Redirect with error: User redirected to your callback URL with error parameters

When errors redirect to your callback URL, your application must handle them and show users an appropriate message.

These errors occur when users navigate to the authorization endpoint with invalid parameters.

When the client_id parameter is missing or references a non-existent app, Vercel shows an error page.

Fix: Verify your client_id matches the ID shown in your app's Manage page.

When the redirect_uri parameter is missing or doesn't match a registered callback URL, Vercel shows an error page.

Fix: Add the redirect URL to your app's Authorization Callback URLs in the Manage page.

When the response_type parameter is missing, Vercel redirects to your callback URL with an error:

https://example.com/api/auth/callback?
  error=invalid_request&
  error_description=Parameter 'response_type'. Required

Fix: Include response_type=code in your authorization request.

When the response_type parameter has an invalid value, Vercel redirects to your callback URL with an error:

https://example.com/api/auth/callback?
  error=invalid_request&
  error_description=Parameter 'response_type'. Invalid enum value. Expected 'code', received 'test'

Fix: Set response_type=code. This is the only supported value.

When the code_challenge parameter is provided but not between 43 and 128 characters, Vercel redirects to your callback URL with an error:

https://example.com/api/auth/callback?
  error=invalid_request&
  error_description=Parameter 'code_challenge'. code_challenge must be at least 43 characters

Fix: Generate a code_challenge that's between 43 and 128 characters long. Follow the PKCE specification for proper implementation.

When the code_challenge_method parameter has an invalid value, Vercel redirects to your callback URL with an error:

https://example.com/api/auth/callback?
  error=invalid_request&
  error_description=Parameter 'code_challenge_method'. Invalid enum value. Expected 'S256', received 'test'

Fix: Set code_challenge_method=S256. This is the only supported value.

When the prompt parameter has an invalid value, Vercel redirects to your callback URL with an error:

https://example.com/api/auth/callback?
  error=invalid_request&
  error_description=Parameter 'prompt'. Invalid enum value. Expected 'consent' | 'login', received 'test'

Fix: Use only consent or login for the prompt parameter. Leave it out if you don't need to control the authorization behavior.