what are http headers
In the field of computer networking , http headers are the key:value pairs send after the requested document location (in http request message ) and status code (in http response message) but before the actual http body content.
http header can be used to define varies parameters during the http transaction, that can affect the client and server communication .
in the http protocol, usually in each http request and http response ,there are many http headers transmitted back and forth, they are in the following format:
The http header section is terminated by a line only composite with a carriage return (CR) and line feed (LF) character sequence.
There are many type of http headers , some of them are standardized by Internet Engineering Task Force in RFC 7230, 7231, 7232, 7233, 7234, and 7235.
Some headers are Non-standard,you can inspect these http header with certain netwok application or web browser extension.you can even send your own http headers if you know how to program and send them
According to the RFCs ,there are no limits restrains to the size of header names and header values, but in practice most web applications such as web browsers and web servers do impose some kind of limitations on these fields, because the limited storage space
The classifications of http headers ,there are general 3 type of http headers , they are
Client sider headers: these headers usually are sent when web client are making request to web servers, typical client http headers include:
Server side headers : these headers that are sent when web server sent message back to the requesting web client, typical server header include:
General headers: the headers that are sent both in http request and http response, usually these headers convey general information or operation directives of http transactions and specific limitation. Typical general headers include: