Video ToolsFree

MP4 to MKV

Convert MP4 videos to MKV (Matroska) format for archiving and media server use. MKV supports multiple audio tracks, subtitle streams, chapter markers, and large file sizes — making it ideal for home media library management with Plex, Jellyfin, or Kodi. No signup.

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MP4, MOV, AVI, MKV, WebM, FLV, WMV, VOB

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Frequently Asked Questions

Why use MKV instead of MP4?▼
MKV (Matroska) supports multiple audio languages, multiple subtitle tracks, chapter markers, and theoretically unlimited file size. It is the preferred format for home media servers (Plex, Jellyfin, Kodi) and high-quality video archiving.
Is there any quality loss converting MP4 to MKV?▼
No. MP4 and MKV are container formats — the video data (H.264, H.265) is the same. The stream is copied directly without re-encoding. Zero quality loss.
Does Plex or Jellyfin prefer MKV over MP4?▼
Both Plex and Jellyfin support MP4 and MKV equally. MKV is often preferred because it better preserves multiple audio tracks and subtitle streams from source video.
Can I add subtitles to the MKV output?▼
Not in this converter. To add subtitle tracks to MKV, use a dedicated tool like MKVToolNix (free, desktop).
Is the conversion done in the browser?▼
Yes. FFmpeg WebAssembly remuxes MP4 to MKV locally without re-encoding. No file is uploaded.