<!DOCTYPE html> <html reftest-async-scroll> <style> body { position: fixed; margin: 0px; top: 0; right: 0; bottom: 0; left: 0; } #scrollbox { width: 100%; height: 100%; overflow: hidden; } #scrolledContents { height: 10000px; background: radial-gradient(circle, blue 30%, transparent 0); background-size: 80px 80px; } </style> <body> <div id="scrollbox" reftest-dislayport-x="0" reftest-displayport-y="0" reftest-displayport-w="800" reftest-displayport-h="2000" reftest-async-scroll-x="0" reftest-async-scroll-y="20"> <div id="scrolledContents"></div> </div> </body> </html>