What's the HTTP_USER_AGENT of browsers in alternative ubuntu distros (Kubuntu, Xubuntu, ...)

Hi,

we want to give the users in our forum the possibility to select the ubuntu version and distro they are using when creating a new topic.
It's our plan to automatically fetch this information from the HTTP_USER_AGENT sent by the browser. This works pretty well for the ubuntu version, but we don't know whether this is possible for the ubuntu distro too. Can anybody tell me what operating system alternative ubuntu distros write into the HTTP_USER_AGENT?

Benjamin Wiegand