IOS6 html hardware acceleration changes and how to fix them (opens in new tab)

In this case, "hardware accelerated" means drawing web content into an offscreen image -- as the content is transformed using CSS, the image is re-drawn and blended using the GPU. This is faster than re-laying-out and re-drawing the web content directly (even if re-drawing the web content itself uses the GPU). It's a good trade-off when you have animations that update every frame.

The biggest cost is memory. Every pixel of hardware accelerated web content gets 4 bytes of memory. This adds up quickly, especially since any content that overlaps hardware accelerated content must become hardware accelerated as well.

The other big cost, as olsn already pointed out, is that blending these offscreen images onto the screen takes time and power on every frame. In extreme cases this can cause scrolling to stutter.

See the "Optimizing Web Content in UIWebViews and Websites on iOS" session from WWDC 2012 for more information about this.

Yes, battery is consumed faster when using the GPU - I cannot tell you by how much, but obviously it is enough on iOS devices for Apple to change its feature sets there.

Not all sites/apps need hardware acceleration and those who do consume a lot more battery. So there is kind of a reason for this - however the way apple implemented this is not from the best quality I think.

The bottom line is, that Apple forces developers to take care of this instead of having everything automatically hardware accalerated and therefore shortening the battery life of iOS devices(by a lot I'm guessing).

agreed. in the release note it says "Authors should stop using this option as a way to get hardware acceleration"... this sounds like there is an other option to do it, does anyone know?

Here's how you make a tasty burger: make a tasty chicken sandwich instead. :P

The issue affects websites as well as hybrid apps. Given that this change is poorly documented by Apple, and it directly affects a JS plugin I'm working on, I'm quite grateful for the OP sharing their findings.

It would, however, indeed be paranoid and crazy.

The WebKit developers spend all day trying to drive the web forward. That's what they do. They're not pulling their punches. Try hanging out in #webkit on irc for a bit and see if you think they want the web to lose to native.