Re: Support for User-Agent?

Andrew Payne (
Mon, 16 May 1994 16:00:52 -0400

> We need the User-Agent header for a number of reasons - most particularly
>for remaining backwards-compatible with older clients as the technology
>continues to develop. I don't believe that Mosaic currently sends it, and I
>know that violaWWW does. What about the other clients? Is there any will out
>there to add this anytime soon?

Mosaic 2.4 sends User-Agent:, and earlier versions may send it as well.

However, it isn't designed for machine consumption. The format isn't
specified, and the HTTP spec even says "This is for statistical purposes and
the tracing of protocol violations." In other words, good luck trying to
guess what the client's capabilities are based on that string.

There are much cleaner ways to deal with backwards-compatibility:

- use new MIME datatypes (for new versions of HTML, for example) in the
request Accept: headers

- Rev. the protocol when it changes. HTTP already has a version number
field that will change when the next version of HTTP comes out.

Is there something that you are trying to do (or a problem that you
anticipate) that doesn't fit into this framework?