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A comment on YouTube change served lower-quality video to Firefox 43 for 2 weeks. Parent comment

Re:YouTube change served lower-quality video to Firefox 43 f... by pdkl95 on Sunday January 10, 2016 @08:15PM (#10878198)
The user agent header should have been dropped a long time ago, as it is one of the largest[1] sources of browser identification data.

Even ignoring the tracking problem, using the user agent string instead of feature detection has always been terrible engineering, as it assumes all browsers within a version have the same features. Browsers have always been configurable - often in extreme ways. I don't understand how anybody can simply6 pretend the preferences dialog (and extensions, etc) doesn't exist.

[1] Out of the 15.91 bits of data that Panopticlick was able to collect from my browser, 9.0 bits (56%) were from the user agent. The 2nd largest source is HTTP_ACCEPT at 4.25 bits.

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Re:YouTube change served lower-quality video to Firefox 43 f... by v413 on Sunday January 10, 2016 @09:23PM (#10878395)
Feature detection is not always enough. E.g. if a browser reports it has a required feature but that feature is buggy rendering it effectively unusable, then browser detection is necessary.
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Re:YouTube change served lower-quality video to Firefox 43 f... by thedufer on Sunday January 10, 2016 @09:08PM (#10878351)
> using the user agent string instead of feature detection has always been terrible engineering

Is there a better solution for server-side feature detection?

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Re:YouTube change served lower-quality video to Firefox 43 f... by davb on Monday January 11, 2016 @02:44AM (#10879429)
Something like the Accept header, listing capabilities. Or something like how Android handles capabilities in manifests.
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Re:YouTube change served lower-quality video to Firefox 43 f... by immibis on Monday January 11, 2016 @03:58AM (#10879669)
BTW, feature detection can be even more identifying (although you need it anyway). IIRC my browser was completely unique at Panopticlick, most likely because I have a rare plugin installed (a handler for byond:// URLs)
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