A Better Method for Embedding YouTube Videos
Compared to the current YouTube card in the Ghost editor, the method provided below saves over 500KB of page load. I tested this on my Ghost site using the same video for both embeds, and here is the Gtmetrix comparison: (GREEN is using the below linked method, and RED is using the built-in Ghost …
<div class="youtube-player" data-id="EhbsiUFL6H8"></div>
<script>

    /* Light YouTube Embeds by @labnol */
    /* Web: http://labnol.org/?p=27941 */

    document.addEventListener("DOMContentLoaded",
        function() {
            var div, n,
                v = document.getElementsByClassName("youtube-player");
            for (n = 0; n < v.length; n++) {
                div = document.createElement("div");
                div.setAttribute("data-id", v[n].dataset.id);
                div.innerHTML = labnolThumb(v[n].dataset.id);
                div.onclick = labnolIframe;
                v[n].appendChild(div);
            }
        });

    function labnolThumb(id) {
        var thumb = '<img src="https://i.ytimg.com/vi/ID/hqdefault.jpg">',
            play = '<div class="play"></div>';
        return thumb.replace("ID", id) + play;
    }

    function labnolIframe() {
        var iframe = document.createElement("iframe");
        var embed = "https://www.youtube.com/embed/ID?autoplay=1";
        iframe.setAttribute("src", embed.replace("ID", this.dataset.id));
        iframe.setAttribute("frameborder", "0");
        iframe.setAttribute("allowfullscreen", "1");
        this.parentNode.replaceChild(iframe, this);
    }

</script>