<!DOCTYPE html> <html class="reftest-wait reftest-no-flush"> <title>Changing keyframes to transform frames creates a stacking context</title> <style> span { height: 100px; width: 100px; position: fixed; background: green; top: 50px; } #test { width: 100px; height: 100px; background: blue; } </style> <span></span> <div id="test"></div> <script> var anim = document.getElementById("test") .animate({ }, { duration: 100000 }); anim.ready.then(function() { anim.effect.setKeyframes({ transform: ['none', 'none'] }); requestAnimationFrame(function() { document.documentElement.classList.remove("reftest-wait"); }); }); </script>