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Comment by decklin | Hacker News Reader

I wonder why browsers with a modern automatic-update process don't set their user-agent to something that discards all this madness ("Chrome/23.4.5678 (Windows)", or similar) for the cutting-edge/nightly builds only (or even betas, if they wanted to discourage casual users from switching to them, but I don't think that's the case at this point). Surely their users have signed up for a little breakage in exchange for the latest features? And if they actually get website operators to stop or at least fix their sniffing, the whole prisoners-dilemma situation would disappear.

(I guess this assumes that the huge user-agent that my Chrome is currently sending is necessarily bad, and in the real world maybe no one really cares...)

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When we actually do this, it does not necessarily convince publishers to fix things. For example: for several months Mozilla has been testing one tiny reduction to the User-Agent string in Firefox Nightly builds (replacing "Gecko/20100101" with "Gecko/16.0"). Zillow.com is the highest-profile site that is broken by this change, and after five months they still haven't even responded to any of our attempts to contact them: http://bugzil.la/754680

It's much better to resist adding things to the UA in the first place, since removing anything later on is a huge pain and inevitably breaks things for users. Mozilla has managed to keep the UA relatively minimal (and successfully reduced it a bit in Firefox 4): https://developer.mozilla.org/en/Gecko_user_agent_string_ref...

Interesting! I wasn't sure if anything like this had been done. I guess it shows that there's nothing good that can come from change here.

I forwarded this on to one of my zillow friends (I used to work there) -- he'll look into it.

Thanks! It looks like it worked. I had even tried contacting @zillow on Twitter, but I hadn't quite reached the point of emailing random engineers. :)

You're implying that if nightly builds of a browser with a simplified UA broke a website that the website owners would fix their code, but that is unlikely to happen. Most websites, particularly the sort with bad UA sniffing, have a high cost to change (engineering, QA, making releases) and no incentive ("it broke on the new Chrome, probably a Chrome bug").

The two instances of UA spoofing I know of in Chrome are for large sites -- hotmail and Yahoo mail. My vague memory of the hotmail case is that Microsoft agreed to fix their code but said it'd take months to make the push. (http://neugierig.org/software/chromium/notes/2009/02/user-ag... , http://neugierig.org/software/chromium/notes/2009/02/user-ag... )

Even a relatively flexible company like Google gets UA sniffing wrong for many of its domains. At one point (as an author of Chrome and an employee of Google) I tried to track down the right people to get things fixed and ran into more or less the above problems. (The non-Chrome non-Safari webkit browsers these days must spoof Chrome to not fall into some "other" browser bucket.)

Ah, the pain of working with the development process of websites. I still remember the Hotmail globalStorage fiasco that led to Firefox 13.0.1 putting it back temporarily: https://bugzilla.mozilla.org/show_bug.cgi?id=736731

1. I think the most interesting thing about that blog post is that it illustrates how the incentives in standards building get warped. I like to describe this sort of thing as "the effect of economics on programming" - not because there is money involved, but because of the nature of the incentives.

2. Graceful degradation. We've sniffed UA's from the minute they were invented. Any change whatsoever would create untold problems for untold millions of people. The UA is just an arbitrary string so… who cares? Very few people (you and I are amongst these "very few") have to be concerned with this compared to the people such a change would affect.

It's because of 1 and 2 (my second point is really an instance of the first) that we're stuck with Javascript. No one in their right mind thinks it's a good language, but getting all the different browser vendors to adopt a good bytecode would be nightmarish (and not necessarily in the interest of every browser vendor).

I think JS is a good language, but I am probably not in my right mind, so touché.

Imagine the problems that would cause! You have Chrome 58 Beta, and stuff works one way. Then they say it's good and release Chrome 58 final, and all of a sudden, stuff changes all over the web.

UA string is just one example of unfortunate hacks that evolved in the web protocols. Compared to probably everything else in HTML it's probably just not even worth it to consider fixing it. We'll always need the old string for compatibility, so it's really only to save a few lines of parsing. Compared to the nightmare of parsing rules for HTTP and HTML, it's not even relevant.

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