This document discusses responsive video formats and codecs for HTML5 video, including MP4, WebM, and Ogg Theora. It provides code examples for using media queries to serve different video sources based on screen width. Formats like H.264, VP8 and Vorbis are supported. Tools like FFmpeg can be used to optimize MP4 files and techniques like Apple HLS and MPEG-DASH enable adaptive streaming. Emerging codecs like ORBX.js, HEVC, VP9 and WebRTC are also mentioned.