Content-Length header
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
The HTTPContent-Length header indicates the size, in bytes, of the message body sent to the recipient.
Content-Length is limited in that the message size must be known up front, before sending the headers, which is a problem when content is dynamically generated or streamed.
- In HTTP/1.0, it is required.
- In HTTP/1.1, it could be replaced with
Transfer-Encoding: chunkedfor responses sent out in parts as its size is calculated. - In HTTP/2,
Content-Lengthis redundant, because the content length may be inferred from DATA frames. It may still be included for backwards compatibility.
Syntax
http
Content-Length: <length>Directives
<length>The length in octets.
Specifications
| Specification |
|---|
| HTTP Semantics # field.content-length |