mkv The Matroska video file format, .mkv, is an open source video file container which is part of the larger open source Matroska Multimedia Container which includes .mka (audio), .mks (subtitles), and .mk3D (stereoscopic video). It was first developed in 2002 and is today favored by many video authors because of the size of produced files. In 2010 the mkv format became the basis of the popular browser independent open format called WebM with several free video players providing playback support for video files encoded in .mkv. Microsoft Windows does not have native support for .mkv video files but there are plans to include native playback support in Microsoft's upcoming operating system Windows 10.
mp4 The MP4 file format and the .mp4 filename extension refer to the MPEG-4 part 14 digital multimedia format developed by the Moving Picture Experts Group. It is used as a multimedia container to wrap encoded digital video and audio streams, including subtitles and still images if required. In recent decades, the format has been popularized as one of the main standards for streaming media over the internet and other computer networks and for the digital distribution of large multimedia files. MP4 supports a large number of compression audio codecs allowing files in this format to maintain a relatively small size without discounting playback quality.