What does HTTP status 511 (Authentication Required) mean?

HTTP_STATUS_AUTHENTICATION_REQUIRED

This status is intended for intercepting proxies such as captive portals, not for ordinary origin-server login. The response can provide a link to a network login page or explain the network access policy.

Applications should detect the captive portal and let the user authenticate through the network workflow. Sending website credentials to the origin will not resolve a 511 generated by an access network.

RFC 6585: Additional HTTP Status Codes

Operational meaning of HTTP 511 for HTTP_STATUS_AUTHENTICATION_REQUIRED

HTTP 511 (HTTP_STATUS_AUTHENTICATION_REQUIRED) is a server-error response. AllStat records its meaning as “511 Network Authentication Required”. For HTTP_STATUS_AUTHENTICATION_REQUIRED, interpret it with the request method, selected representation, response headers, and the specification or product that defines the code; the number alone does not prove that application work completed.

Client and server handling for HTTP_STATUS_AUTHENTICATION_REQUIRED

• Correlate HTTP_STATUS_AUTHENTICATION_REQUIRED with origin, gateway, load-balancer, and dependency logs to locate which hop generated it.
• For HTTP_STATUS_AUTHENTICATION_REQUIRED, record request and trace identifiers, upstream timing, retry count, and the health of the selected backend.
• For HTTP_STATUS_AUTHENTICATION_REQUIRED, use bounded retries with backoff only for idempotent work and only when the service policy permits them.

For telemetry, record HTTP 511, method, authority, route template rather than secrets, response headers relevant to caching or retry, latency, upstream identity, and whether the response originated at the application or an intermediary.

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