HTTP: The Definitive Guide

Protocol Versions

There are several versions of the HTTP protocol in use today. HTTP applications need to work hard to robustly handle different variations of the HTTP protocol. The versions in use are:

HTTP/0.9

The 1991 prototype version of HTTP is known as HTTP/0.9. This protocol contains many serious design flaws and should be used only to interoperate with legacy clients. HTTP/0.9 supports only the GET method, and it does not support MIME typing of multimedia content, HTTP headers, or version numbers. HTTP/0.9 was originally defined to fetch simple HTML objects. It was soon replaced with HTTP/1.0.

HTTP/1.0

1.0 was the first version of HTTP that was widely deployed. HTTP/1.0 added version numbers, HTTP headers, additional methods, and multimedia object handling. HTTP/1.0 made it practical to support graphically appealing web pages and interactive forms, which helped promote the wide-scale adoption of the World Wide Web. This specification was never well specified. It represented a collection of best practices in a time of rapid commercial and academic evolution of the protocol.

HTTP/1.0+

Many popular web clients and servers rapidly added features to HTTP in the mid-1990s to meet the demands of a rapidly expanding, commercially successful World Wide Web. Many of these features, including long-lasting “keep-alive” connections, virtual hosting support, and proxy connection support, were added to HTTP and became unofficial, de facto standards. This informal, extended version of HTTP ...