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MKV → MP4

MKV to MP4 Converter

Play a Matroska file on any phone, TV or editor. If the MKV already holds H.264 and AAC, the conversion takes seconds.

FreeNo sign-upNo upload — runs on your device

Drop a MKV file here, or click to browse

Accepted: .mkv · up to 2 GB

Conversion mode

Before you start

  • · The first conversion downloads the FFmpeg engine (about 32 MB). It is cached afterwards.
  • · Keep files under 2 GB, and under a few hundred MB if you are on a phone or re-encoding video.
  • · Keep this tab in the foreground — browsers throttle background tabs and the conversion will pause.

How to convert MKV to MP4 in 3 steps

  1. 1

    Add your MKV file

    Drop in a .mkv file from a media library, a physical-disc rip or a download.

  2. 2

    Pick remux or re-encode

    Fast remux is the default and handles most MKV files. Choose Re-encode when the video is HEVC or AV1, or the audio is DTS, TrueHD or AC-3.

  3. 3

    Convert and download

    Press Convert. Video and audio are copied or converted, then muxed into a faststart MP4 ready for any player.

About MKV and MP4

Why MKV will not play everywhere

Matroska is a remarkably capable container: multiple audio tracks, subtitles, chapters, any codec you like. That flexibility is the problem. Phones, smart TVs, consoles and video editors often refuse MKV outright or support only a subset, so a file that plays perfectly on a computer with VLC can be completely unplayable on a television or a phone.

Remux versus re-encode, in practice

Most MKV releases already contain H.264 video and AAC audio, which is exactly what MP4 expects. For those, remuxing just rewrites the container and the result is identical in quality at a speed limited only by disk I/O. Files built on HEVC, AV1 or 10-bit video, or on DTS and TrueHD audio, cannot be copied into MP4 — those need the re-encode mode, which trades time for compatibility.

What happens to subtitles and extra tracks

This converter keeps the first video stream and the first audio stream. Subtitle tracks, chapter markers and secondary audio languages are not carried into the MP4, because the common MP4 subtitle format is far more restrictive than Matroska’s and silently dropping tracks is worse than admitting it. If you need burned-in subtitles, treat that as a separate job.

Frequently asked questions

How do I convert MKV to MP4 for free?
Add the MKV file above, keep Fast remux selected, and press Convert. It is free with no account, no watermark and no length limit beyond memory.
What is the difference between remux and re-encode?
Remux copies the existing video and audio streams into a new container without touching them, so it is fast and lossless. Re-encode decodes and recompresses everything, which is slower but works with codecs MP4 cannot hold.
My MKV has 5.1 DTS audio and the MP4 has no sound — why?
MP4 cannot carry DTS. Use the Re-encode mode, which converts the audio to stereo AAC, or accept an audio-less MP4 if the source is the problem.
Will subtitles be included?
No. The converter keeps the first video and first audio stream only. Matroska subtitles do not map cleanly onto MP4, so they are left out rather than silently mangled.
Can I convert a 4K MKV in the browser?
Remuxing a 4K MKV is fine because nothing is decoded. Re-encoding 4K in WebAssembly is impractical — both too slow and beyond the 32-bit memory ceiling.
Are my video files uploaded?
No. The MKV is read and converted entirely inside your browser, so nothing is sent to a server.

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