Convert MP4 to MKV — The Home Theater Container for Plex and Kodi
MKV (Matroska) is built for maximum flexibility — it holds multiple audio tracks, multiple subtitle tracks, chapters, and attachments in a single file. Converting MP4 to MKV is how home theater enthusiasts pack multiple language audio tracks and subtitle options into one file that Plex, Kodi, and Jellyfin serve with full track selection.
MKV: The Home Theater Container for Plex and Kodi
MP4 is a standardized container designed for broad compatibility — it works everywhere but limits you to two audio tracks and doesn't support complex subtitle formats. MKV (Matroska Video) is an open container with no such restrictions: embed 10 language audio tracks, 20 subtitle tracks (SRT, ASS, PGS), chapter markers, and cover art in a single file. Plex, Kodi, and Jellyfin all treat MKV as first-class. The conversion from MP4 to MKV is a lossless remux — your video and audio streams are copied unchanged into the new wrapper, with no re-encoding and no quality change.
How to Convert MP4 to MKV
Click "Convert Now" — opens the video converter with MP4 → MKV pre-selected.
Drag and drop your .mp4 file or click Browse. Any H.264 or H.265 MP4 works.
FFmpeg.wasm performs a lossless container remux entirely in your browser — no re-encoding, no server upload.
Your MKV file downloads automatically, ready to add to your Plex, Kodi, or Jellyfin library.
Why Convert MP4 to MKV?
- 🔊 MKV holds unlimited audio tracks — store multiple language dubs (English, Spanish, French) in one file
- 💬 Subtitle tracks embed directly — SRT, ASS, and PGS subtitle tracks live inside the MKV container
- 📺 Plex, Kodi, and Jellyfin direct-play MKV natively — full track selection in the media server UI
- 📖 Chapters and metadata embed cleanly — scene navigation works in all MKV-capable players
- 🆓 Open standard — no licensing fees or proprietary restrictions on MKV playback or creation
MP4 vs MKV — Format Comparison
MP4 (MP4 (MPEG-4 Part 14)) and MKV (Matroska Video (.mkv)) use different compression and storage methods. The table below shows the key technical differences. MP4/H.264 is the dominant video format for web and device playback. MKV supports multiple audio tracks, subtitles, and chapters. A pure container format.
Features
Lossless Remux
Video and audio copied unchanged — no re-encoding, no quality change, completed in seconds.
100% Private
Your video never leaves your device. No upload, no cloud processing.
Plex & Kodi Ready
MKV is the preferred format for Plex, Kodi, and Jellyfin home theater servers.
Subtitle Support
MKV supports SRT, ASS, and PGS subtitle tracks for full home theater subtitle selection.
Free
No account, no fee, no watermarks. Unlimited conversions.
Works on Mobile
Convert on your phone or tablet — no desktop app needed.
Key Questions About MP4 to MKV, Answered
Direct answers structured for AI extraction, voice search, and featured snippets.
Will my video be re-encoded or just remuxed when converting MP4 to MKV?
Always a remux. Matroska natively supports both H.264 and H.265 — the only two codecs MP4 commonly uses — so Convertlo simply repackages the existing video and audio streams into an MKV wrapper without touching the actual data.
- H.264-in-MP4 → MKV: remuxed, instant, zero quality loss
- H.265-in-MP4 → MKV: remuxed, MKV natively supports HEVC
- The conversion is essentially just relabeling the container
What are the track-limit differences between MP4 and MKV containers?
MP4 handles one or two audio streams and struggles with complex subtitle formats, while MKV has no practical track limits — it can bundle dozens of audio tracks, subtitle streams in any format, and chapter files in one file.
- MP4 audio: typically 1–2 tracks; MKV: unlimited (common for Blu-ray rips with 5+ language tracks)
- MP4 subtitles: TTXT or VTT only; MKV supports SRT, ASS, PGS, VobSub, and more
- MKV also supports ordered chapters, attached fonts, and complex chapter menus
How much will the file size change going from MP4 to MKV?
Since the conversion is a remux, the file size stays essentially the same — only the container wrapper changes, not the actual video or audio data.
- H.264/H.265-in-MP4 → MKV: size unchanged (remux)
- Any size difference comes from minor container overhead, not re-encoding
- To actually shrink the file, re-encode to H.265 or VP9 rather than just changing the container
Why do Kodi and Plex prefer MKV over MP4 for home theater setups?
Kodi and Plex rely on audio passthrough for Dolby TrueHD, DTS-HD MA, and Atmos — MKV is the container that most reliably carries those lossless audio formats to an AV receiver without transcoding.
- Dolby TrueHD, DTS-HD MA, Atmos: supported in MKV; MP4 can hold them but passthrough breaks on many setups
- MKV stores subtitle streams as PGS or ASS — better sync and styling than MP4's TTXT
- Both containers use H.264/H.265 video, so picture quality is identical
Go Deeper: MP4 to MKV Resources
In-depth articles to help you understand the formats, pick the right settings, and get the best results.