WebM is a multimedia container format meant to provide a royalty-free, high-quality open video compression format for replacements with HTML5 video. The project's development is sponsored by Google. A WebM file contains VP8 video and Vorbis audio streams, in a very container based on a profile of Matroska. The project releases WebM related software within BSD license and many types of users are granted a worldwide, non-exclusive, no-charge, royalty-free patent license.

WebM is definitely an audio-video container format created to provide royalty-free, open video compression for replacements with HTML5 video. The WebM Project releases WebM-related software within a BSD license and all sorts of users are granted an internationally, non-exclusive, no-charge, royalty-free patent license.

The WebM container will be based upon a profile of Matroska. WebM initially supported VP8 video and Vorbis audio streams. In 2013 it turned out updated to allow for VP9 video and Opus audio.