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I feel like User-Agent in general is not well suited to the modern web. Most browsers pretend to be some version of Mozilla or Netscape. And most things that

by g82918 7y ago

I feel like User-Agent in general is not well suited to the modern web. Most browsers pretend to be some version of Mozilla or Netscape. And most things that scrape sites like Apple's messaging app pretend to be something equally outdated. Deprecating User-Agent seems like the best course of action in the long run.

judge2020 7y ago
Relevant https://webaim.org/blog/user-agent-string-history/ https://webaim.org/blog/user-agent-string-history/
rictic 7y ago
I'd be happy for the User-Agent string to die (or be frozen in amber), but I want the ability to have a rough sense of the capabilities of a browser in order to determine what JS I should send down to them. Like, if you're on IE11 I can send down code that's compiled to ES5 and has all the polyfills you need, and if you're on almost any other browser I just need some signal that you've got a reasonably up to date version and I can send down a much smaller and more optimal JS file. Maybe runtime browser-side feature detection can be fast enough. I haven't benchmarked. The other tricky thing that User-Agent strings are good for is working around browser bugs. Every once in a while a browser will ship with a totally broken language feature that's essentially impossible to detect at runtime. A particularly bad example was from an old version of Edge, which had a JIT bug where class constructors could – in very particular circumstances – return the class object itself rather than an instance of the class. In that situation, if you want your site to work you have to detect that version of Edge and treat it like IE: send it the bigger, more compatible blob rather than code for modern browsers.
tzs 7y ago
I'd be OK with getting rid of User-Agent if some kind of "capabilities supported" header were added. Something like Agent-Capabilities: 1; 97464bde5d94a54f6e199309489a4b60 where the 97464bde5d94a54f6e199309489a4b60 is a set of bit flags in hex, each representing some feature, and the 1 before the semicolon is a version number for the bit definitions. The assignment of these flags would have to be standardized. When new versions of HTML, CSS, or JavaScript are standardized, that would include assigning bits for their new features, and bumping the bit definition version number. You might say that it is better to do run-time checks on the client for features you want, and have the client then load workarounds if necessary for missing features, and that indeed is a good way to go in many cases (maybe even most cases). That method, though, only works going forward. Sometimes I want to know what capabilities past visitors to my site have had. For example, I'm going to be redoing some pages at work and want to know if I can require certain CSS and JavaScript and HTML features. I could make a list of the features I want to use, add some JavaScript to those pages to test for those, and send the results back to the server...and then I'd have to wait weeks or months or longer to get a good idea of what the consequences would be of requiring those features. With User-Agent strings, all I had to do was pull up the site logs. Our shopping cart logs the User-Agent string, and page flow through the cart. It was an easy matter to pull up the last 18 months of those logs, and write a script to find all the successful orders and make a table showing how many there were for each browser. (I limited it to successful orders, because those would almost certainly all be real people in regular browsers that are reasonably honest about the User-Agents). I could then look up the features I was interested in on https://caniuse.com/ https://caniuse.com/ and see which of the features were not on browsers that we still get significant traffic through. Dropping User-Agent without adding something to allow that kind of analysis, such as Agent-Capabilities, would be very annoying.
OliverJones 7y ago
This got me to thinking how my stuff uses User-Agent. I'm not in a datahoovering biz. Still, we've always believed, rightly, that we need User-Agent to help us troubleshoot users' problems. Mostly, the questions we asked of it were "Internet Explorer or not? If so, what version?" Let's throw down this challenge to the browser companies: MAKE YOUR STUFF SOLID ENOUGH AND STANDARD ENOUGH THAT WE DON'T NEED User-Agent.

by g82918 7y ago

judge2020 7y ago

Relevant https://webaim.org/blog/user-agent-string-history/ https://webaim.org/blog/user-agent-string-history/

rictic 7y ago

I'd be happy for the User-Agent string to die (or be frozen in amber), but I want the ability to have a rough sense of the capabilities of a browser in order to determine what JS I should send down to them. Like, if you're on IE11 I can send down code that's compiled to ES5 and has all the polyfills you need, and if you're on almost any other browser I just need some signal that you've got a reasonably up to date version and I can send down a much smaller and more optimal JS file. Maybe runtime browser-side feature detection can be fast enough. I haven't benchmarked. The other tricky thing that User-Agent strings are good for is working around browser bugs. Every once in a while a browser will ship with a totally broken language feature that's essentially impossible to detect at runtime. A particularly bad example was from an old version of Edge, which had a JIT bug where class constructors could – in very particular circumstances – return the class object itself rather than an instance of the class. In that situation, if you want your site to work you have to detect that version of Edge and treat it like IE: send it the bigger, more compatible blob rather than code for modern browsers.

tzs 7y ago

I'd be OK with getting rid of User-Agent if some kind of "capabilities supported" header were added. Something like Agent-Capabilities: 1; 97464bde5d94a54f6e199309489a4b60 where the 97464bde5d94a54f6e199309489a4b60 is a set of bit flags in hex, each representing some feature, and the 1 before the semicolon is a version number for the bit definitions. The assignment of these flags would have to be standardized. When new versions of HTML, CSS, or JavaScript are standardized, that would include assigning bits for their new features, and bumping the bit definition version number. You might say that it is better to do run-time checks on the client for features you want, and have the client then load workarounds if necessary for missing features, and that indeed is a good way to go in many cases (maybe even most cases). That method, though, only works going forward. Sometimes I want to know what capabilities past visitors to my site have had. For example, I'm going to be redoing some pages at work and want to know if I can require certain CSS and JavaScript and HTML features. I could make a list of the features I want to use, add some JavaScript to those pages to test for those, and send the results back to the server...and then I'd have to wait weeks or months or longer to get a good idea of what the consequences would be of requiring those features. With User-Agent strings, all I had to do was pull up the site logs. Our shopping cart logs the User-Agent string, and page flow through the cart. It was an easy matter to pull up the last 18 months of those logs, and write a script to find all the successful orders and make a table showing how many there were for each browser. (I limited it to successful orders, because those would almost certainly all be real people in regular browsers that are reasonably honest about the User-Agents). I could then look up the features I was interested in on https://caniuse.com/ https://caniuse.com/ and see which of the features were not on browsers that we still get significant traffic through. Dropping User-Agent without adding something to allow that kind of analysis, such as Agent-Capabilities, would be very annoying.

OliverJones 7y ago

This got me to thinking how my stuff uses User-Agent. I'm not in a datahoovering biz. Still, we've always believed, rightly, that we need User-Agent to help us troubleshoot users' problems. Mostly, the questions we asked of it were "Internet Explorer or not? If so, what version?" Let's throw down this challenge to the browser companies: MAKE YOUR STUFF SOLID ENOUGH AND STANDARD ENOUGH THAT WE DON'T NEED User-Agent.