<!DOCTYPE html>
<title>Client Hint Echoing Iframe</title>
<body>
<script>
window.parent.postMessage({'headers': {
    'sec-ch-viewport-width': '{{header_or_default(sec-ch-viewport-width, )}}',
    'sec-ch-ua-reduced': '{{header_or_default(sec-ch-ua-reduced, )}}',
    'sec-ch-ua-mobile': '{{header_or_default(sec-ch-ua-mobile, )}}',
}}, '*');
</script>
</body>
