Convert MP4 to MKV — Free Online Converter

MP4 to MKV conversion repackages your MPEG-4 video into the Matroska container format. MKV is an open-standard container that can hold virtually unlimited numbers of video, audio, and subtitle tracks in a single file. Unlike MP4, which has restrictions on supported codecs, MKV accepts everything from H.264 and H.265 to VP9, AV1, FLAC, DTS, and bitmap subtitles.

Our converter performs a stream copy by default — remuxing the existing video and audio streams from the MP4 into an MKV container without re-encoding. This is essentially instant and produces zero quality loss. The MKV container adds support for features like ordered chapters, soft subtitles in ASS/SSA format, and multiple audio tracks.

MKV is the format of choice for media archivists and home theater enthusiasts. It supports features that MP4 cannot: multiple subtitle tracks in various formats (SRT, ASS, VobSub), lossless audio codecs (FLAC, DTS-HD MA, TrueHD), chapter navigation with ordered chapters, and tagging systems for detailed metadata. If you are building a media library managed by Plex, Jellyfin, or Kodi, MKV is the preferred container because it holds all tracks in one file without compromise.