Google announced that it is now defaulting to the HTML5 player on the web for YouTube embeds, moving to iframes. Along with this, they're deprecating the "old style" of Flash <object> embeds and their Flash API.
The company is encouraging all embeddes to use the iframe API, which as it notes, can inelligently use whichever technology the client supports. Google says in a blog post:
Four years ago, we wrote about YouTube’s early support for the HTML5 <video> tag and how it performed compared to Flash. At the time, there were limitations that held it back from becoming our preferred platform for video delivery. Most critically, HTML5 lacked support for Adaptive Bitrate (ABR) that lets us show you more videos with less buffering.
Over the last four years, we’ve worked with browser vendors and the broader community to close those gaps, and now, YouTube uses HTML5 <video> by default in Chrome, IE 11, Safari 8 and in beta versions of Firefox.
The benefits of HTML5 extend beyond web browsers, and it's now also used in smart TVs and other streaming devices.
Google credits technologies like MediaSource extensions the VP9 codec, encrypted media extensions and common encryption, WebRTC, and Fullscreen with progressing HTML5 video. As it notes, other companies like Netflix, Vimeo, Microsoft, and Apple have all embraced HTML5.
Google also credits HTML5 with enabling new classes of devices such as Chromebooks and Chromecast.
The company tells developers to support HTML5 by using the iframe API everywhere you embed videos on the web.