MKV (Matroska Video) is an open-source video container format developed in 2002. It's widely used for storing high-quality video, particularly ripped or downloaded movies and TV shows, because it can hold virtually any combination of video, audio, and subtitle tracks in a single file.
Unlike MP4, MKV imposes almost no restrictions on the codecs or number of tracks it can contain. A single MKV file can include multiple audio languages, multiple subtitle tracks, and chapter markers - making it popular for home media servers like Plex and Jellyfin.
The main trade-off between MKV and MP4 is flexibility versus compatibility. MKV supports more codecs and features, but MP4 has far broader device support. Most Smart TVs, phones, and streaming platforms handle MP4 natively, while MKV may require a dedicated media player or conversion first.
MKV is the standard format for high-definition video archives, Blu-ray rips, and media server libraries. It's less common for sharing or uploading, where MP4 is preferred.
MKV files can range from very large (lossless or high-bitrate encodes) to relatively small, depending entirely on the codec and settings used. The container itself adds no overhead - file size is determined by the content inside.
You can convert MKV to MP4 directly in your browser - no software to install, no upload required. Your file never leaves your device.