Files with the .WEBM extension contain compressed video and audio data in a high quality, open WebM format. The compression the data is subjected to is called VP8 for the video and Ogg Vorbis for the audio. The format is based on the Matroska – MKV - video container.

WEBM video are often used to present films on HTML5-based web pages – specifically using the <video> tag. Most web browsers support this format as part of the HTML5 technology. It is an open alternative to the patented h.264 and MPEG4 standards, so it can be used in both commercial and non-commercial applications.