HTTP 511 Network Authentication Required
Updated Free mock REST & WebSocket APIs
HTTP 511 Network Authentication Required — The client must authenticate to gain network access (captive portal).
- Class
- 5xx Server Error
- Defined in
- RFC 6585
- Official
- Yes (IANA registry)
- Cacheable by default
- No (unless Cache-Control/Expires say so)
- Safe to retry
- Sometimes — idempotent requests only
Try it: get a real 511 response
Our test endpoint answers every request with 511 Network Authentication Required.
curl -i https://mockfox.dev/api/status/511Use it in tests, health-check monitors or to see how your client handles a 511. Add ?delay=2000 to slow it down.
What does HTTP 511 mean?
Sent by captive portals — hotel, airport and café Wi-Fi — that intercept traffic until you log in or accept terms. It tells software that the response isn't from the site it asked for. Open any http:// page in a browser to get the login page; operating systems detect captive portals automatically.
How to fix 511
- Visitors: This is a server-side problem — wait a moment and retry, or check the site's status page.
- Developers: Check application and proxy logs at the time of the error, verify upstream services are healthy, and alert on 5xx rates.
Example 511 response
HTTP/1.1 511 Network Authentication Required
Content-Type: text/html
Content-Type: application/json
{"status":511,"error":"Network Authentication Required"}5xx Server Error: The server failed to fulfill a valid request — usually temporary, or a server-side bug. See the full list of HTTP status codes.
Related status codes
- 401 UnauthorizedThe request lacks valid authentication credentials; it must include a WWW-Authenticate challenge.
- 407 Proxy Authentication RequiredLike 401, but the client must first authenticate with the proxy in between.
- 403 ForbiddenThe server understood the request but refuses to authorize it.
Related tools
Frequently asked questions
What does HTTP 511 Network Authentication Required mean?
The client must authenticate to gain network access (captive portal).
Is 511 a client or a server error?
511 is a 5xx code: the server failed to handle a request that may be perfectly valid. It's often temporary.
Where is 511 defined?
In RFC 6585. It's listed in the IANA HTTP Status Code Registry.
How can I test how my app handles a 511?
Call https://mockfox.dev/api/status/511 — it responds with 511 to any method, with CORS enabled. Add ?delay=2000 to simulate a slow response.