...ProgressBar.js is lightweight, MIT licensed and supports all major browsers including IE9+. A simple code example of creating a Line shaped progress bar and animating it from 0% to 100%. ProgressBar.js uses shifty tweening library to animate path drawing. So in other words, animation is done with JavaScript using requestAnimationFrame. Animating with JS gives more control over the animation and is supported across major browsers. For example IE does not support animating SVG properties with CSS transitions.