AMP (Accelerated Mobile Pages)

<!doctype html>
<html amp lang="en">
<head>
    <meta charset="utf-8">
    <script async src="https://cdn.ampproject.org/v0.js"></script>
    <title>Hello, AMPs</title>
    <link rel="canonical" href="https://amp.dev/documentation/guides-and-tutorials/start/create/basic_markup/">
    <meta name="viewport" content="width=device-width,minimum-scale=1,initial-scale=1">
    <script type="application/ld+json">
        { "@context": "http://schema.org", "@type": "NewsArticle", "headline": "Open-source framework for publishing content", "datePublished": "2015-10-07T12:02:41Z", "image": [ "logo.jpg" ] }
    </script>
    <style amp-boilerplate>
        body {
            -webkit-animation: -amp-start 8s steps(1, end) 0s 1 normal both;
            -moz-animation: -amp-start 8s steps(1, end) 0s 1 normal both;
            -ms-animation: -amp-start 8s steps(1, end) 0s 1 normal both;
            animation: -amp-start 8s steps(1, end) 0s 1 normal both
        }

        @-webkit-keyframes -amp-start {
            from {
                visibility: hidden
            }
            to {
                visibility: visible
            }
        }

        @-moz-keyframes -amp-start {
            from {
                visibility: hidden
            }
            to {
                visibility: visible
            }
        }

        @-ms-keyframes -amp-start {
            from {
                visibility: hidden
            }
            to {
                visibility: visible
            }
        }

        @-o-keyframes -amp-start {
            from {
                visibility: hidden
            }
            to {
                visibility: visible
            }
        }

        @keyframes -amp-start {
            from {
                visibility: hidden
            }
            to {
                visibility: visible
            }
        }
    </style>
    <noscript>
        <style amp-boilerplate>
            body {
                -webkit-animation: none;
                -moz-animation: none;
                -ms-animation: none;
                animation: none
            }
        </style>
    </noscript>
</head>
<body>
    <h1>Welcome to the mobile web</h1>
    <script async custom-element="amp-analytics" src="https://cdn.ampproject.org/v0/amp-analytics-0.1.js"></script>
    <amp-analytics type="googleanalytics" id="analytics">
        <script type="application/json">
        {
            "vars": {
                "account": "UA-XXXXXXXX-Y"
            },
            "triggers": {
                "trackPageviewWithAmpdocUrl": {
                    "on": "visible",
                    "request": "pageview",
                    "vars": {
                        "title": "TITLE",
                        "ampdocUrl": "CANONICAL_URL"
                    }
                }
            }
        }
        </script>
    </amp-analytics>
</body>
</html>

https://amp.dev/documentation/guides-and-tutorials/start/create/basic_markup/

https://github.com/ampproject/amphtml/blob/master/spec/amp-var-substitutions.md