HTTP 561 – Unauthorized
(AWS ELB) The load balancer's built-in authentication (e.g. for OIDC or Cognito) rejected the request.
Common use case
Appears when an Application Load Balancer configured with built-in user authentication (via Amazon Cognito or an OIDC provider) rejects a request that failed that authentication step.
History
An AWS-specific extension for ALB authentication failures.
Did you know?
It is easy to confuse with the standard 401 Unauthorized, but this one is generated by the load balancer itself, before the request ever reaches the application.