I was grappling with background-attachment: fixed in iOS devices just last week… caniuse.net indicated that it’s supported now, but that is very much still not the case.<p>I think I’ve finally cracked why it’s not supported. The official line is that it’s “too expensive” on the cpu, but that doesn’t hold water when single-core performance of iPhones regularly outpaces Macs.<p>iOS Safari does one extra “abstraction” phase of an entire web page that allows for instant pinching and zooming of web pages. In order to get background-attachment: fixed working under such a paradigm, you would need to not only calculate where the background image is relative to the viewport, but also the size and placement of a zoomed document in real time. And on top of that, the browser designers would need to make some kind of decision on what a coherent implementation of the feature would even do under such circumstances.<p>I wish that iOS had a way to just turn off this extra abstraction in CSS altogether. It was a fine crib before responsive design was a thing, but for some pages, it just causes problems now. It’s not needed “everywhere” on the web any more than it’s necessary in all iOS apps.