Convert AAC to MKV — Free Online Converter

AAC is a standard lossy audio codec, while MKV (Matroska Video) is an open-source multimedia container capable of holding unlimited audio, video, subtitle, and chapter tracks in a single file. Converting AAC to MKV wraps the audio in Matroska's flexible container, which is useful when combining audio with other media tracks or when your media pipeline expects MKV input.

MKV is the preferred container for archivists and media enthusiasts because of its ability to hold multiple tracks, chapters, and attachments. If you are building an MKV media file and need to add AAC audio to it, or if your media server (Plex, Jellyfin, Kodi) processes MKV files more efficiently, wrapping AAC in MKV can be beneficial. MKV also supports advanced features like ordered chapters and segment linking that no other container offers.

FFmpeg muxes the AAC stream into a Matroska container using stream copy — no re-encoding occurs. MKV natively supports AAC audio, so the bitstream is preserved. MKV's flexible header allows adding chapter markers, track metadata (language, default/forced flags), and codec-specific initialization data. The file can later accept additional video or subtitle tracks via mkvmerge.