MP4 to MKV Converter

Runs in your browser — your files are never uploaded.

Convert MP4 to MKV. Matroska is the flexible container of choice for media servers and home libraries — Plex, Jellyfin and Kodi all favour it, and it handles multiple audio tracks, subtitles and chapters that MP4 struggles with. The conversion is normally lossless and quick, because the existing streams are repackaged rather than re-encoded.

OptionsResolution: Original

How to convert MP4 to MKV

  1. 1

    Drop your .mp4 file onto the box, or click to choose one.

  2. 2

    OkConverter loads the conversion engine (one-time per session) and repackages the streams.

  3. 3

    Click “Download” to save the .mkv file.

Share

Embed this tool on your site

Paste this where you want the tool to appear. It runs entirely in your visitor's browser — no uploads, no account, no tracking.

Please keep the attribution line — it's what keeps these tools free.

Need a different size, a dark theme, or a different tool? Build an embed lets you preview it first.

Frequently asked questions

Does this re-encode the video?+

Not usually. MKV can hold practically any codec, so the H.264 video and AAC audio from your MP4 are copied across untouched — lossless, and about as fast as copying the file.

Why would I want MKV over MP4?+

Multiple audio tracks, embedded subtitles and chapter markers, which MP4 handles poorly or not at all. It is the standard for media-server libraries. For sharing on phones and social platforms, stay with MP4.

Can I add subtitles with this tool?+

Not currently — this converts the container only. It gives you an MKV that a tool like MKVToolNix can then merge subtitle tracks into.

Is my video uploaded anywhere?+

No. Once the engine has loaded, the repackaging happens entirely inside your browser tab.

Related conversions