HTTP 411 Length Required
Updated Free mock REST & WebSocket APIs
HTTP 411 Length Required — The server refuses a request with a body but no Content-Length header.
- Class
- 4xx Client Error
- Defined in
- RFC 9110 §15.5.12
- Official
- Yes (IANA registry)
- Cacheable by default
- No (unless Cache-Control/Expires say so)
- Safe to retry
- Not without changing the request
Try it: get a real 411 response
Our test endpoint answers every request with 411 Length Required.
curl -i https://mockfox.dev/api/status/411Use it in tests, health-check monitors or to see how your client handles a 411. Add ?delay=2000 to slow it down.
What does HTTP 411 mean?
Some servers (and older proxies) require a Content-Length and won't accept chunked transfer encoding. Fix it by sending the length — most HTTP clients do this automatically when the body is a string or buffer rather than a stream. Also seen when a POST is sent with no body and no Content-Length: 0.
How to fix 411
- Visitors: Reload the page, check the address for typos, and clear the site's cookies. If it persists, the site owner needs to fix it.
- Developers: Read the response body and server logs for details, fix the request (method, headers, body, credentials) and return a clear error message to clients.
Example 411 response
HTTP/1.1 411 Length Required
Content-Type: application/json
{"status":411,"error":"Length Required"}4xx Client Error: The request contains an error or can't be fulfilled — fix the request before retrying. See the full list of HTTP status codes.
Related status codes
- 413 Content Too LargeThe request body is larger than the server is willing to accept.
- 400 Bad RequestThe server can't process the request because it's malformed or invalid.
Related tools
Frequently asked questions
What does HTTP 411 Length Required mean?
The server refuses a request with a body but no Content-Length header.
Is 411 a client or a server error?
411 is a 4xx code, so it signals a problem with the request (as seen by the server). Retrying the identical request usually gives the same result.
Where is 411 defined?
In RFC 9110 §15.5.12. It's listed in the IANA HTTP Status Code Registry.
How can I test how my app handles a 411?
Call https://mockfox.dev/api/status/411 — it responds with 411 to any method, with CORS enabled. Add ?delay=2000 to simulate a slow response.