Does Draggable use CSS3 animations or transitions for the motion?

Nope. CSS3 transitions and animations have some significant limitations that make them ill-suited for the type of motion that these tools require, so highly optimized JavaScript is used instead. In order to tap into GPU compositing, 3D transforms are used when possible (in browsers that support them) and updates are made using requestAnimationFrame (when available) for maximum efficiency. See for yourself in Chrome Dev Tools - you should see very snappy performance in the timeline. Many other tools like jQuery UI use top/left properties for positioning which don't generally perform as well. These tools have been fully "GreenSocked" so performance is smoking fast, just like the core tweening engine.

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Does Draggable use CSS3 animations or transitions for the motion?