As per modern web dev standards: you should always use feature detection not agent sniffing to handle cross browser issues; however having accurate user agent detection is really handy for trouble shooting customer issues, bot detection, spotting trends etc.
The user agent string definitely has a place on the web, the problem is that it's been used and abused by web developers in the 90s and 2000s when trying to deal with the utter mess that was "browser compatibility" back then.
I run whatismybrowser.com and it's a perfect case of why user agents are useful information. It'll tell you what browser you've got, what OS, and whether you're up to date or not. It's extremely useful to know this info when helping non-tech users - you would not believe how many people still reply "I just click the internet" when you ask them what browser they're using. My site helps answer all those complicated "first" questions.
I completely agree that using User Agents for feature detection/brower compatibilty is a terrible idea, but apparently enough websites still do it to warrant having to keep all that useless, contraditory mumbo jumbo in it too - it isn't what they should be used for any more!
And also, I don't think there's any problem with including "too much" information in the user agent either - point in case: Firefox used to include the full version number of Firefox in the user agent, but now it only shows the major version number, not the exact revision etc. The problem is I can no longer perfectly warn users if they're actually up to date or not.
The reasoning for this is given as a security concern, which I still don't understand - if there's a security problem in a particular point-revision version of Firefox which can be exploited by a malicious web server - odds are they're just going to try that exploit for any version of firefox and it either will or won't work - how does the malicious site knowing the exact version make the situation any worse?!
Wow, the example in the article is an extremely verbose error message! But still, detailed and helpful error messages really do make the developer's life easier.
When building API end points, I take a different approach by including both messages and message codes, as well as a general "result" code (to make it easy to determine if it's a basic success/error result (also including the right HTTP code)).
An example that I'm working on right at the moment:
{
"result": {
"code": "error",
"message_code": "too_many_user_agents",
"message": "You have sent %s user agents; this is more than the maximum allowed per batch (%s user agents). Please send fewer in each batch."
}
}
The message describes the problem; what they did wrong, what the limit is and how they can fix it so it doesn't happen again.
As well as this, the developer can easily check that the response code was an error, and there's the message_code - this will NEVER EVER change for this problem, so a developer could write code to specifically deal with that scenario.
However there's also a human readable message, which may potentially change (perhaps a grammar or punctuation fix, or if it included a URL it might change one day...)
I've found this approach is the best sort of middle ground.
This is more of a technique for learning than for practice... but one thing that I make a habit of when learning a new programming framework is deliberately typing out sample code that I've found in books or online instead of just copying and pasting it.
It's the equivalent of writing out notes by hand from a school textbook instead of just photocopying the pages... some how the process of actually re-typing it out causes it to stick in my mind better. And then later, when you're really "in the zone", you don't break your focus by needing to keep referring back to the book, it's already embedded in your muscle memory and you just keep plowing away.
Great technique recommendation. I make it a practice to never copy-paste an answer from StackOverflow. I always type it out by hand to grasp the meaning of each line of code properly. It's anecdotal, but I strongly feel it helps me absorb new languages and frameworks faster (and deeper).
Not useless. I type out code from books but resort to pencil when the snippets I find difficult; that way, I can annotate and manipulate the code more intensely.
I'm obsessed with speed on my main site (whatismybrowser.com) so I simply use default system fonts, in order to minimise HTTP requests and download time.
It's quicker to just use system fonts than have to have the user make a trip to Google's Font Servers.
It made it easy to help someone find their local ip address, without having to click around in settings or the command line:
https://www.whatismybrowser.com/detect/what-is-my-local-ip-a...
But I understand the fingerprinting/privacy concerns, so it's for the best that it's not available.