WebM File Format
WebM is an audio-video format designed to provide royalty-free, open video compression for use with HTML5 video. The project's development is sponsored by Google Inc. WebM is based on two open codecs for compressing the video and audio component of the content. .webm file stores video compressed using VP8 technology and audio compressed using Ogg Vorbis compression.
WebM file format aim to develop a high-quality, open video format for the web that's freely available to everyone. Most major Web browsers will support WebM as part of HTML5 video delivery. WebM video format is compatible with commercial and non-commercial applications. In computer, you can use VLC media player, Flash Player or Web browsers like Mozilla Firefox, Opera, Chrome to open and play WebM video. YouTube offers WebM videos as part of its HTML5 player experiment in 360p, 480p, 720p and 1080p resolutions.
WebM Compression: MP4 vs WebM /