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411 Length Required

4xx client error

The server refuses the request because it has no Content-Length header.

411 means the server wants to know the size of the body up front and won't accept a request without Content-Length — for example one sent with chunked transfer encoding. It mostly comes from older servers, some proxies, and endpoints that must know the size before accepting data.

Class4xx Client Error
Retry?No — change the request first
Cacheable by defaultNo — only with explicit Cache-Control
Response bodyAllowed
Defined inRFC 9110 §15.5.12 — 411 Length Required
Example response
HTTP/1.1 411 Length Required
Content-Type: application/json
Content-Length: 27

{"error":"Length Required"}

Common causes

  • A POST or PUT sent with chunked transfer encoding to a server that doesn't support it.
  • An empty-body POST sent without Content-Length: 0.

How to fix it

  1. Send Content-Length, including Content-Length: 0 for empty bodies.
  2. Buffer the body before sending if your client streams it in chunks.

Send a 411 from your server

Express
res.status(411).json({ error: "Length Required" });
Next.js route handler
return Response.json({ error: "Length Required" }, { status: 411 });
Flask
return {"error": "Length Required"}, 411
Go net/http
http.Error(w, "Length Required", http.StatusLengthRequired)
nginx
return 411;

Check what a URL returns

Print just the status line from the command line, or check a whole list of URLs at once, with their response headers, in the HTTP Status Checker.

curl -sI https://example.com/your-path | head -n 1

Frequently asked questions

Why does my empty POST get 411?

Some servers and proxies require Content-Length even when there's no body. Send Content-Length: 0 or an explicit empty body.

Headers used with 411
Related status codes