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HTTP Status Code
411 Length Required
Client ErrorThe server requires a Content-Length header but the request did not include one.
HTTP status code reference, response example, common causes, fixes, and related status codes.
What does HTTP 411 Length Required mean?
HTTP 411 Length Required is a status code sent by a server to indicate the result of an HTTP request.
Status codes help browsers, APIs, apps, and backend systems understand whether a request succeeded, failed, was redirected, or needs additional action.
In practice, HTTP 411 Length Required usually appears when a server responds under specific request, validation, permission, or infrastructure conditions.
Response example
HTTP/1.1 411 Length Required
HTTP example
HTTP/1.1 411 Length Required
Relevant headers
Content-Length
Content-Length: 123
Common causes
- Missing Content-Length header
- Server requires explicit body size
How to fix it
- Add a valid Content-Length header
- Let the HTTP client compute it automatically when possible
Common mistakes
- Assuming the status code alone explains the full backend issue
- Ignoring related response headers that add important context
- Treating temporary errors as permanent failures
- Retrying too aggressively without checking the cause
- Debugging the frontend only when the problem is server-side
How browsers and APIs use it
Browsers, APIs, and backend services use HTTP status codes to understand the outcome of a request. Depending on the status code, an application may render content, retry a request, redirect the user, show an error, or trigger a different flow in the client or server.
Developer note
Modern browsers and fetch usually handle Content-Length automatically, but lower-level clients or proxies can still trigger 411.