<!DOCTYPE html> <meta charset="utf-8"> <title>CSS Cascade: 'revert' keyword in transition</title> <link rel="author" title="Emilio Cobos Álvarez" href="mailto:emilio@crisal.io"> <link rel="author" title="Mozilla" href="https://mozilla.org"> <link rel="help" href="https://drafts.csswg.org/css-cascade/#default"> <script src="/resources/testharness.js"></script> <script src="/resources/testharnessreport.js"></script> <style> html, body { margin: 0 } h1 { margin: 0; transition: margin 10s; transition-delay: -5s; /* So we can expect it to be half-way the transition when toggling the property */ } </style> <h1>This is a header that should get some margin</h1> <script> test(function() { const el = document.querySelector("h1"); const cs = getComputedStyle(el); assert_equals(cs.marginTop, "0px", "Margin before transition"); el.style.margin = "revert"; const midTransition = cs.marginTop; assert_not_equals(midTransition, "0px", "Margin mid transition"); el.style.transition = "none"; assert_not_equals(cs.marginTop, midTransition, "Default margin"); }, "revert works with transitions"); </script>