Ideal if you don't have Flash Player installed in your device. I know I don't.
// ==UserScript==
// @name Replace old Flash Player-based YouTube embeds by their new HTML5 counterparts
// @description Ideal if you don't have Flash Player installed in your device. I know I don't.
// @namespace greasyfork.org/users/4813-swyter
// @include *
// @version 2016.01.03
// @noframes
// @grant none
// @run-at document-start
// @icon https://i.imgur.com/L2y0zMj.png
// ==/UserScript==
/* wait until the page is ready for the code snipped to run */
document.addEventListener('DOMContentLoaded', function()
{
/* iterate over all the existing SWF Youtube players in the page */
for (var cur in (vids=document.querySelectorAll('object > embed[src*="youtube"]')))
{
console.log(vids[cur], typeof vids[cur]);
/* create the HTML5 player element */
iframe = document.createElement('iframe');
iframe.src = 'https://www.youtube.com/embed/' + vids[cur].src.split('?')[0].split('/')[4];
/* keep their same size */
iframe.width = vids[cur].width;
iframe.height = vids[cur].height;
/* no borders plz, thanks! */
iframe.setAttribute("frameborder", 0);
/* replace the old SWF Flash object with it, voilà */
vids[cur].parentNode.parentNode.replaceChild(iframe, vids[cur].parentNode);
}
}, false);