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