This method of embedding seems to be functioning well on all browsers except for Firefox; I took advantage of a free trial at crossbrowsertesting.com to verify. I’m not using a direct iFrame embed, and all the solutions I’ve come across are related to that particular issue. The method I am utilizing is detailed in this article: A Better Method for Embedding YouTube Videos on your Website.
It displays the thumbnail image of a YouTube video, and only loads the actual video player when the user clicks on the thumbnail manually.
The nearest relevant topic I found on Stack Overflow was about YouTube embed not working in Firefox, but it didn't address my specific situation.
Here are screenshots showing correct display on Chrome:
https://i.stack.imgur.com/XVWyE.jpg
And incorrect display on Firefox:
https://i.stack.imgur.com/cOeEi.png
In the Firefox snapshot, you can observe the margin appearing as I hover over that <div>.
Setting an explicit height value does make the thumbnail visible in Firefox, but it compromises the responsiveness of the method.
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);
}.youtube-player {
position: relative;
padding-bottom: 56.23%;
/* Use 75% for 4:3 videos */
height: 0;
overflow: hidden;
max-width: 100%;
background: #000;
margin: 5px;
}
.youtube-player iframe {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
z-index: 100;
background: transparent;
}
.youtube-player img {
bottom: 0;
display: block;
left: 0;
margin: auto;
max-width: 100%;
width: 100%;
position: absolute;
right: 0;
top: 0;
border: none;
height: auto;
cursor: pointer;
-webkit-transition: .4s all;
-moz-transition: .4s all;
transition: .4s all;
}
.youtube-player img:hover {
-webkit-filter: brightness(75%);
}
.youtube-player .play {
height: 72px;
width: 72px;
left: 50%;
top: 50%;
margin-left: -36px;
margin-top: -36px;
position: absolute;
background: url("//i.imgur.com/TxzC70f.png") no-repeat;
cursor: pointer;
}<div class="youtube-player" data-id="VIDEO_ID"></div>