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Asset Compressor

Convert MKV to MP4

MKV is great for storing video but many TVs, phones and editing apps won’t open it. Remux it to MP4 in seconds without touching the picture quality.

  • No upload
  • No watermark
  • No file size limit
  • Hardware accelerated

Drop videos here to convert them

MP4, MOV, WebM, MKV, AVI and more · no size limit or watermark

Processed on your device. Your videos are never uploaded.

Output format

MP4 with H.264 plays on every phone, computer, TV and social network.

Compression

Keeps the original video stream when the format allows it – fast and lossless. Otherwise it re-encodes at high quality.

Resolution
Exact size & social formats

Applies to the shorter side, so 720p works for landscape and vertical videos. Smaller videos are never enlarged.

Advanced: codec, frame rate, audio, trim
Video codec

Auto picks the most compatible codec your browser can encode. H.265 and AV1 are smaller but play on fewer devices.

Frame rate
Audio
Trim

Use m:ss or seconds. Applies to every video in the list.

How to convert MKV to MP4

  1. 1

    Add your MKV files

    Drop in one or more .mkv videos.

  2. 2

    Keep MP4 and “Original” quality

    H.264 and HEVC video is copied straight into MP4 without re-encoding.

  3. 3

    Convert

    Remuxing only rewrites the container, so it usually finishes in seconds.

  4. 4

    Download

    Save the MP4 files individually or as a ZIP.

MKV versus MP4

Matroska (MKV) is an open container that can hold almost any video and audio codec, several audio languages and subtitles. MP4 is less flexible but supported by nearly every device and app. When the MKV contains H.264 or HEVC video – as most do – converting to MP4 is just a change of container.

Remuxing explained

Remuxing copies the compressed video and audio into a new container without decoding them. There is no quality loss and the file size stays about the same. If the audio is in a format MP4 players handle poorly, such as AC-3, DTS or Opus, only the audio is converted to AAC.

Tracks and subtitles

Asset Compressor keeps the main video track and the main audio track. Additional audio languages, subtitle tracks and chapters are not copied into the MP4.

Playing MKV files on TVs and phones

Many smart TVs, game consoles and phone galleries can’t open MKV even when they support the video codec inside it. After remuxing to MP4 the same video usually plays directly from a USB stick, a phone gallery or a media server, with no change in picture quality.

Frequently asked questions

Will converting MKV to MP4 reduce quality?

Not for H.264 or HEVC video: the video stream is copied unchanged. Only videos in other codecs are re-encoded, at high quality.

Why does conversion take longer for some MKV files?

When the audio or video must be re-encoded – for example surround sound in DTS, which browsers can’t decode – Asset Compressor uses its slower compatibility engine.

Are subtitles kept?

No. Subtitle tracks are not copied. If you need them, keep the MKV or use a desktop tool to burn them in.

Are my files uploaded?

No. Everything happens locally in your browser.

Can I convert several MKV files at once?

Yes. Add as many as you like. They are converted one after another and can be downloaded together as a ZIP.

Related tools

Video converter

Change a video’s format in seconds. When the codecs allow it, the streams are copied without re-encoding, so the quality stays exactly the same.

MOV to MP4

iPhones and QuickTime save videos as MOV. Turn them into MP4 files that play on Windows, Android and every website – usually without re-encoding.

Compress video

Shrink MP4, MOV, WebM and MKV files on your own device with hardware-accelerated encoding. Choose a quality level or an exact target size – no upload, no watermark.

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