List of HTTP headers

HTTP Headers form the core of an HTTP request, and are very important in an HTTP response. They define various characteristics of the data that is requested or the data that has been provided.

This is an incomplete list of some of the HTTP headers defined in RFC 2616 and RFC 2109 for HTTP/1.1

Requests

Responses

Effects of selected HTTP headers

Cache-Control

If the server responds with Cache-Control: no-cache then in particular a web browser must not cache the object. In a web browser one effect of this is that if one returns to a previous web page by clicking on the back button, then, if that page was sent with the Cache-Control: no-cache directive, the browser will request the page again. This introduces latency. Depending on the situation this may or may not be appropriate. During a login session it is likely that caching is undesirable since pages may contain sensitive data. Therefore, by default in PHP, during a session, the Cache-Control header will be set to prevent caching.

References

ee also

* List of HTTP status codes
* ETag

External links

* [http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html HTTP/1.1: Header Field Definitions]
* [http://www.and.org/texts/server-http HTTP/1.1 headers from a web server point of view]
* [http://url-info.appspot.com/ HTTP Header Viewer with Google App Engine]