<!doctype html><title>CSS Values and Units Test: rem units on the root element</title><linkrel="help"href="https://drafts.csswg.org/css-values/#rem"><scriptsrc="/resources/testharness.js"></script><scriptsrc="/resources/testharnessreport.js"></script><style>:root{font-size:50px;margin-left:2rem;padding-top:2rem;line-height:2rem;}</style><script>letrootStyle=getComputedStyle(document.documentElement);test(()=>assert_equals(rootStyle.marginLeft,"100px"),"rem based margin.");test(()=>assert_equals(rootStyle.paddingTop,"100px"),"rem based padding.");test(()=>assert_equals(rootStyle.lineHeight,"100px"),"rem based line-height.");test(()=>{document.documentElement.style.fontSize="initial";letinitialFontSize=parseInt(getComputedStyle(document.documentElement).fontSize);document.documentElement.style.fontSize="3rem";assert_equals(getComputedStyle(document.documentElement).fontSize,3*initialFontSize+"px");},"Check that rem font-size is based on the initial font-size.");</script>