HTTP Versions

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The initial version of HTTP seen on the web was HTTP/0.9, which contained only the most basic functionality for retrieving mainly static resources from a web server. This evolved into the HTTP/1.0 specifications that were issued as "Informational" only. The reasons for this were because of perceived scale and performance issue. However in real terms, implementation of the HTTP/1.0 (unofficial) standard was varied and there were almost as many versions as there were HTTP/1.0 products.

With the introduction of the HTTP/1.1 standard, the implementation of HTTP became somewhat more standardised (perhaps because it is a wider, more comprehensive protocol definition), but still varies to some extent from vendor to vendor. Coupled with this is still the fact that there are many HTTP clients and servers in use still supporting a variant of HTTP/1.0.

The HTTP standards are backwards compatible so any remaining clients supporting the initial HTTP/0.9 standard will continue to work, albeit with limited functionality.

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