411

Length Required

4xx Client Error

ELI5

You're trying to send me something, but you didn't tell me how big it is. I need to know the size before I can accept it.

Server perspective

Use 411 when the server refuses to accept the request without a defined Content-Length.

When to use

•Return 411 when the endpoint requires a known body length in advance
•Use it when chunked or streaming request semantics are not accepted for that operation
•Server requires Content-Length for processing
•Upload endpoints that need size validation
•Streaming requests without proper headers
•Security policies requiring content length

How to respond

•Explain that Content-Length is required
•Document whether chunked transfer encoding is supported as an alternative

Headers to consider

•Content-Length

Response body

•Optionally include a concise error explaining that an accepted Content-Length or transfer mode is required.

Server-side pitfalls

•Do not require Content-Length when your server already supports the transfer mode being used
•Do not use 411 for requests that do not meaningfully send a body
•Chunked transfer encoding is supported
•GET requests (no body expected)
•Content size is properly specified

Examples

File upload without Content-Length

Request:POST https://api.example.test/api/upload

Response:

411 Length Required

# Headers
Content-Type: application/json

# Body
{
  "error": "content_length_required"
}

Server requires Content-Length header to process the upload

References

Related Status Codes

Bad Request

Your request doesn't make sense or has mistakes in it. Check what you're sending and try again.

Content Too Large

The file or data you're trying to send is too big for me to handle. Please make it smaller.