HTML5 video
Support for HTML5 video has been steadily increasing. In June 2013, Netflix added support for HTML5 video. In January 2015, YouTube switched to using HTML5 video instead of Flash by default. In December 2015, Facebook switched from Flash to HTML5 for all video content.
BrowserQuest
"BrowserQuest" is written in HTML5 and WebSockets and is playable from modern web browsers. The client makes use of HTML5's canvas element to render the graphics, web workers to initialize the map without affecting the rest of the page, localStorage to save progress, media queries to dynamically resize the game to the device, and HTML5 Audio to render the sound. The server uses node.js communicating with the browser using WebSockets. "BrowserQuest" is a demonstration of the technology that it uses.