I recall reading someone complaining about Apple adding this feature. Unlike normal vendor prefixes, it's not really for an experimental feature that other vendors might implement, it's a final feature that is proprietary.
It'd be foolish to use it on the broader web (and I don't know any instances of anyone doing so), but it seems like it could be really useful for HTML intended to be rendered in an app on an Apple platform.
A brief Googling didn't make it clear to me whether Android has the option to set global text size or, if it does, whether it matches Apple's scheme sufficiently well that it'd make sense to have a common specification for this.
That's a lot like saying that after searching the Usenet, you didn't find that IE supported the <blink> tag, while Netscape did :)
Android should let you set system font sizes. It's a usability thing. And if Apple, Google, and MS can agree on how this is done, that'd be a good thing for everyone involved.
From my understanding - it is proprietary at the moment but Apple has publicly pushed for other vendors to do something similar and for it to be standardized. There is a discussion on w3c to make this a standard: https://lists.w3.org/Archives/Public/www-style/2015Jul/0169....
I get that this is proprietary - but I do like the idea of font styles being driven by global user settings at the browser or system level. Would love to see more of this in the future.
I put this together mostly so that I could build some simple iOS prototypes with html and css - not something I'd use for the average web app project.
My parents can't use a few applications because of designers refusal. My dad literally had to change banks because some of the banks used too small fonts. So far none of them use dynamic type, but at least some have larger fonts.
