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Content-Length Header

Indicates the size of the request or response body in bytes.

Header TypeBidirectional (Request/Response)
SpecificationStandard RFC compliant
Associated CodesHTTP 411,HTTP 413

What is the Content-Length header?

The Content-Length header indicates the size of the payload body in decimal number of octets (bytes) sent to the recipient.

API Usage & Best Practices

  • Validate request sizing: Gateways check this header to immediately reject payloads exceeding limits with a 413 Payload Too Large.
  • Reject missing lengths when body is expected: If a POST or PUT request expects a body but the header is omitted entirely (chunked or streamed without it), return a 411 Length Required. An explicit Content-Length: 0 is a valid, empty body — not a missing header — and shouldn’t trigger 411.

Examples

POST /v1/leads HTTP/1.1
Content-Type: application/json
Content-Length: 124

Associated HTTP Status Codes

HTTP 411 — Length Required

The server refuses to accept the request without a defined Content-Length header.

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HTTP 413 — Content Too Large

The request body size exceeds the maximum limit allowed by the server.

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