RE: Browsing the Web with a non-existing User-Agent

Part of the reason for differentiating on User Agent rather than Accept is (as most adaptation solution providers know) you can't always trust the Accept header. The other part is that the Accept header doesn't tell you much about how the agent will present the content. A clue to that is the User Agent header, with which you can look up a repository of previously recorded device information. And if your repository is packed with device information, you might as well add in the details of what content types the device supports. So the Accept header becomes redundant.

Of course, a good adaptation mechanism should be able to deal with completely unknown devices based solely on the Accept header, to at least deliver a "functional user experience". Thus, from the POV of a client designer, there is good reason to include the User Agent and Accept header in the request. If only they'd stop saying they accept "*/*"!

Our MIS adaptation technology, and that of other professional solutions, will gracefully degrade its response as the device evidence is constrained. Sites that use such technology will therefore not break when Francois arrives with his crazy browser configurations. But, as Jo says, there are plenty out there using some home-brew or less-than-adequate solutions that can give unacceptable user experiences in these circumstances. Such circumstances are not always contrived, because we regularly observe unusual user agent behaviour with new devices on the market. The nature of our MIS device handling process ensures that users of new devices will still get a good experience, and we get a little bit of time to make that experience perfect for the next product release/update.

It would be interesting to see a report from Francois summarising the results of his survey, assuming the sample size is high enough. Though I'd advise making the tested sites anonymous, as they probably could do without the bad publicity :)


-----Original Message-----
From: [] On Behalf Of Jo Rabin
Sent: 01 October 2008 20:10
To: Francois Daoust
Cc: public-bpwg-ct
Subject: Re: Browsing the Web with a non-existing User-Agent

If you don't supply a User-Agent at all a lot of sites break, according 
to some stuff I did a while ago.

But yes, this is at the heart of what we are trying to establish. If, as 
a Content Provider, you do differentiate on User Agent and not Accept 
then that's interesting and that's what we are in the game to promote, I 
think. I'm sorry that it's not more prevalent in your sample, Francois.


On 01/10/2008 15:53, Francois Daoust wrote:
> I've been masquerading my User-Agent header lately to browse the Web, 
> using a non-existing User-Agent with no link whatsoever to any existing 
> one.
> I was expecting to see things break one way or the other, but the thing 
> is I had no real problem so far.
> I see a few sites that return an "application/vnd.wap.xhtml+xml" 
> content-type that is not recognized by my browser, but this typically is 
> an indication that they have a mobile-optimized version, so not what I 
> would consider to be a big problem.
> So I'm wondering. Can anyone point out a few web sites that returns a 
> rejected response when queried with a "weird" User-Agent? (either 
> through a 406 status, or through a 200 status code with a "sorry" 
> message) I suppose I'm only browsing modern Web sites, not "legacy" ones.
> Thanks,
> Francois.

Received on Thursday, 2 October 2008 09:09:16 UTC