How can I autoplay a video using the new embed code style for Youtube?

You need to add an extra parameter, alongside the autoplay=1

allow="autoplay"

making it:

<iframe src="your-video-url?rel=0&amp;controls=0&amp;showinfo=0&amp;autoplay=1" frameborder="0" allow="autoplay; encrypted-media"></iframe>

Chrome blocks audio content being played without any user interaction.

So, a work-around is to start the video muted by adding

&mute=1

This will work 100% of the time.

Okay this is an example for the new embed code for youtube videos.

<iframe title="YouTube video player" class="youtube-player" type="text/html" width="560" height="345" src="http://www.youtube.com/embed/8v_4O44sfjM" frameborder="0" allowFullScreen></iframe>

if you want to autoplay it, at the src="http://www.youtube.com/embed/8v_4O44sfjM" add the ?autoplay=1 parameter

So the code will look like this:

<iframe title="YouTube video player" class="youtube-player" type="text/html" width="560" height="345" src="http://www.youtube.com/embed/8v_4O44sfjM?autoplay=1" frameborder="0" allowFullScreen></iframe>

i tried this on my blog and it works ! Hope this help (:

YouTube auto play works only desktop in need to work mobile just make changes in JavaScript. Like

<div id="player"></div>
                    var tag = document.createElement('script');
                    tag.src = "https://www.youtube.com/iframe_api";
                    var firstScriptTag = document.getElementsByTagName('script')[0];
                    firstScriptTag.parentNode.insertBefore(tag, firstScriptTag);
                    var player;
  function onYouTubeIframeAPIReady() {
    player = new YT.Player('player', {
      videoId: 'VideoID',
      playerVars: {   
            'autoplay': 1,   
            'rel': 0,
            'showinfo': 0,
            'modestbranding': 1,
            'playsinline': 1,
            'showinfo': 0,
            'rel': 0,
            'controls': 0,
            'color':'white',
            'loop': 1,
            'mute':1,
            // 'origin': 'https://meeranblog24x7.blogspot.com/'
      },
      events: {
        'onReady': onPlayerReady,
        // 'onStateChange': onPlayerStateChange
      }
    });
  }
  function onPlayerReady(event) {
    player.playVideo();
    player.mute();
  }var done = false;
  function onPlayerStateChange(event) {
    if (event.data == YT.PlayerState.PLAYING && !done) {
      setTimeout(stopVideo, 6000);
      done = true;
    }
  }
  function stopVideo() {
    player.stopVideo();
  }

 

See More :- YouTube auto play for 5 seconds

It's not working since April of 2018 because Google decided to give greater control of playback to users. You just need to add autoplay=1&mute=1 to your URL. Autoplay Policy Changes

<iframe id="existing-iframe-example"width="640" height="360"
  src="https://www.youtube.com/embed/-SFcIUEvNOQ autoplay=1&mute=1&enablejsapi=1" frameborder="0"
style="border: solid 4px #37474F"></iframe>

You can get more detail from the already submitted answer YouTube Autoplay not working