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

From: Francois Daoust <fd@w3.org>
Date: Thu, 02 Oct 2008 14:30:23 +0200
Message-ID: <48E4BEDF.2030103@w3.org>
To: Jo Rabin <jrabin@mtld.mobi>
CC: Rotan Hanrahan <rotan.hanrahan@mobileaware.com>, public-bpwg-ct <public-bpwg-ct@w3.org>

Just to clarify.

I am not running a survey.

I was indeed looking for examples to what Jo mentions as b) (How many 
sites respond with "Your browser is not supported" when faced with a 
User-Agent they don't recognize, rather than an unacceptable Accept 
configuration).

Since I didn't have any example and was not in a hurry, I thought the 
best way was to change the User-Agent string my desktop browser is using 
to some weird-looking one (I use the name of a young French singer for 
teenagers, because that's the only thing that crossed my mind at the 
time...), and see some "sorry, not supported" messages here and there.

It's been a week, I've just been browsing my regular web sites: news, 
travel, banking, blogs, search engines, yellow pages, videos, merchants 
sites, weather. I haven't tried any adult related site yet, but I'll 
give it a try!

I would not call that a survey, certainly wouldn't say it's 
representative of the Web at large, I do not consider myself to be a 
browse-addict, and I haven't been assembling any stats out of it. I have 
not seen any "sorry, not supported" message yet, and that's the reason 
why I raised the question.

I forgot that the list was public, and mentioning names and URIs here 
may indeed not be suitable here. It certainly was not my intention to 
point out to someone and say: your site breaks and it's bad. Well, we do 
say that 406 responses are good anyway, don't we?

Anyway, I didn't have any second thought when sending my initial 
message, but... since we seem to be having troubles to assemble any 
stats on this, maybe we could all change our User-Agent while browsing 
with our favorite desktop browser, and try to build a (private) list of 
10 mainstream sites that return rejected responses. A kind of 
implementation report on the use of 406-like responses. Is it a stupid idea?

Francois.


Jo Rabin wrote:
> 
> Thanks Rotan
> 
> Yes, interesting point about the type of site.
> 
> Given that the types of site you mention are likely to have specific 
> mobile tailored interfaces you'd especially want them not to be 
> transformed by an in-network proxy and so if a transforming proxy 
> "remembers" the sites that return 406 or 200 with "browser not 
> supported" I guess that they'd have to remember the precise user agent 
> that was not supported, rather than making the blanket assumption that 
> the site was looking to see a desktop user agent string.
> 
> Hmmm, I can see some more editorial work coming up to make that point 
> clear.
> 
> Jo
> 
> 
> 
> 
> On 02/10/2008 12:31, Rotan Hanrahan wrote:
>> Hi Jo,
>>
>> Certainly. It's good to get a sense of the true picture in the Web 
>> regarding how user agents are handled. Regarding motivation b) such a 
>> response might be given in some security and access-control 
>> circumstances, and in the mobile space you may find it when you try to 
>> download incompatible ringtones/apps. (Of course, you shouldn't even 
>> be offered incompatible material.) Eliminating the security and 
>> resource download use cases, you're left with the ordinary "pages", 
>> presumably with the usual HTML, XHTML, cHTML, MP, WML etc formats. I 
>> can't recall any details regarding the prevalence of 406 errors when 
>> surfing for these ordinary pages, so the research from Francois in 
>> this area would be interesting.
>>
>> What I'm suggesting is that the figures you get on 406 errors can be 
>> influenced by the types of site you include in the survey. If you 
>> include a higher percentage of sites that offer ringtones, wallpaper, 
>> mp3, apps etc, then you might have a significantly higher occurrence 
>> than if you just surfed at random.
>>
>> ---Rotan.
>>
>> -----Original Message-----
>> From: Jo Rabin [mailto:jrabin@mtld.mobi] Sent: 02 October 2008 12:04
>> To: Rotan Hanrahan
>> Cc: public-bpwg-ct
>> Subject: Re: Browsing the Web with a non-existing User-Agent
>>
>> Hi Rotan
>>
>> There are a couple of different things we are trying to establish. a) 
>> How many sites provide a different user experience based upon the 
>> content of the User-Agent, and b) How many sites respond with "Your 
>> browser is not supported" when faced with a User-Agent they don't 
>> recognise, rather than an unacceptable Accept configuration.
>>
>> We want to know b) because if the number is vanishingly small then 
>> there is strong reason for the CT Guidelines to say *never* change the 
>> User Agent string, but it is permissible to change the Accept(-*) 
>> headers to avoid this kind of 406 response.
>>
>> If it is not true then there is strong justification for saying "try 
>> with unaltered User Agent first, then try with a vanilla one", which 
>> is what the CT Guidelines draft says at present, and which several 
>> Last Call comments have pointed to.
>>
>> I'm aware of a number of sites that reject requests from IE and a few 
>> that reject requests because the browser says it is not IE.
>>
>> On a) we want to know that, well, for pleasure, really. To know that 
>> the mantra of custom sites for different types of devices is making 
>> headway. The really important thing at the moment is to understand how 
>> prevalent 406 because of User Agent is ...
>>
>> All best
>> Jo
>>
>>
>>
>> On 02/10/2008 10:07, Rotan Hanrahan wrote:
>>> 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 :)
>>>
>>> ---Rotan.
>>>
>>> -----Original Message-----
>>> From: public-bpwg-ct-request@w3.org 
>>> [mailto:public-bpwg-ct-request@w3.org] 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.
>>>
>>> Jo
>>>
>>> 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 12:31:10 GMT

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