HTTP 511 — Network Authentication Required

Server error responses (5xx) · Updated 2026-10-18

HTTP 511 is the captive-portal code: the network itself demands login before any traffic passes, and this response intercepts the client’s first request to redirect it to the sign-in page.

When 511 shows up

• Hotel and airport Wi-Fi login intercepts.
• Corporate guest networks requiring terms acceptance.

Mocking a 511 response

A response with this status can be faked end to end with a local mock rule — no backend changes needed. The configuration below mirrors the rule fields the ApiSimul editor uses (method, path, status, delay in milliseconds, response body):

{
  "method": "GET",
  "path": "/connect",
  "status": 511,
  "delay": 220,
  "enabled": true,
  "body": {
    "error": "network_auth_required",
    "portalUrl": "https://portal.example.com"
  }
}

Dynamic placeholders such as {{random.name}}, {{string.uuid}} or {{number.int 1 100}} can appear inside the body to vary each response, which keeps client-side list rendering and retry logic honest during development.

Frequently asked questions

What does HTTP 511 mean?
Network access requires authentication before real requests can pass. Completing the portal login clears the interception.

How can I test a 511 response without a real backend?
Define a mock rule with the method and path your client requests and set the status to 511. The example configuration above returns this response after the listed delay, so the client exercises its 511 handling exactly as it would against a live server.

Related status codes

Need the response in your own project? Spin up rules for any status with the ApiSimul mock server, or browse every status code page.