Similarly, Mozilla recently had to freeze part of Firefox’s User-Agent string because some websites mistook Firefox 110 as IE 11 and blocked access because they no longer supported IE 11. The websites misinterpreted “rv:110” in Firefox’s Use-Agent string as “rv:11”.
Or worse, Opera users will change their user agent string to Mozilla so as not to have to deal with ua-sniffing websites that work fine on Opera but warn you anyway about using a unsupported browser.
Sadly, this behavior is somewhat common for many sites that block firefox based on the user agent. At least form some webcompat bug issues I've looked at.
Frankly, Firefox should take the nuclear option, and just start emulating Chrome with regard to website identifiable information.
In particular, User-Agent strings are now a net-negative. I've never run into a website that doesn't work on Firefox. I do occasionally run into websites that claim to not work on Firefox. We software developers have shown that we can't be trusted with information pertaining to what browser someone is using, and as such should have the privilege taken away. If you're reading this, and you have access to a codebase that reads User-Agent strings for anything more than idle curiosity, just delete it and push to master.
It's the severely-outdated Firefox version number. Spambots and crawlers sometimes have user-agent strings corresponding to very old browsers, because they were set once when the bot was created and then never updated. On an unrelated site that I run, we get a lot of traffic with user agent strings corresponding to implausibly-old browsers, and it's ~100% bots.
"Your user-agent string specifies your browser as being a variant of FIREFOX.
Judging by your fingerprint we believe your browser is a variant of FIREFOX.
Your user-agent string specifies your operating system as being a variant of UNKNOWN.
Judging by your fingerprint we believe your operating system is a variant of WINDOWS."
And yet
User agent is parsed as "Mozilla/5.0 (X11; OpenBSD amd64; rv:49.0) Gecko/20100101 Firefox/49.0 SeaMonkey/2.46". Which is actually the case.
Yeah, aren't we just making things a lot more messy? Especially if we're not planning on removing the User-Agent header?
This pattern keeps repeating itself, freeze "Mozilla/5.0", start changing "Chrome/71.1.2222.33", freeze that, start changing "Sec-CH-UA", etc. Browsers will start needing to fake "Sec-CH-UA" to get websites to work properly, etc.
"> Microsoft also included the command "Like Gecko" which instructs the website to send back the same version of the website as they would to Firefox"
This is a little misleading. "Like Gecko" is not used in the Firefox UA String. It just says Gecko. "Like Gecko" is a component of Webkit-based browsers. So IE is emulating Webkit emulating Firefox, and dries the "MS" of "MSEI" for their string, and going with just "IE".
How is that a bug when they say that's what the spec says. Also, both Edge and WebKit are going to adopt that behaviour since it makes sense.
I think there's one more reason people see less of Firefox. I know a LOT of people who have set their user agent string to Chrome to stop the idiotic banners on websites telling me to use Chrome even through the website works perfectly on FF. I hate it even more when websites simply won't allow me to load the page when I'm on FF.
That nightmare had to do with misbehaving servers. IE had to advertise as Mozilla so servers would serve the better response.
In this case it would be possible for a client to fake a UA, but it's more likely that they weren't aware they were doing things incorrectly and correct the behavior rather than opting in to mimicing a different UA to get the server to behave in a non-standard way.
I haven't seen this happen, and this is one of the most popular DAV implementations. I have seen people fix broken implementations as I've slowly been making the server more strict over the last 10 years.
Nah, there's plenty of examples of sites breaking on Firefox. For example, the recent degraded performance on Youtube linked to Firefox User Agent strings.
It astonished me that the people who wrote the CDC covid tracker made it refuse Firefox visitors through User Agent checks. Mozilla had to add an intervention to spoof UA's, specifically on that site:
I presume that would unfortunately break websites in _other_ ways, if they're UA-sniffing Firefox in unconventional ways. At that point they might as well remove it altogether instead of drastically changing the UA string.
https://bugzilla.mozilla.org/show_bug.cgi?id=1805967
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