Skip to content
All video conversions

MKV to MP4 converter

Convert MKV to MP4 in your browser. No upload and no account: the file never leaves your device, so the only size limit is your device’s memory.

I want MP4
Quality

Applies only when the video has to be re-encoded. A straight copy keeps the original quality.

Advanced 2
Always re-encode Rebuilds the picture as H.264 (VP9 for WebM) even when it could be copied. Fixes files that won’t play on older TVs and PCs.

Bytes of your files sent anywhere: 0 B

Related conversions

Need it the other way round? Convert MP4 to MKV

Other ways to convert MKV

Convert other formats to MP4

Read more about the MKV format and the MP4 format, or see every video tool and all video conversions.

Should you convert MKV to MP4?

MKV files play in VLC but not on iPhones, most TVs, editors or upload forms. MP4 is the format everything accepts.

Usually a quick, safe conversion. MP4 can carry H.264, HEVC (H.265), VP9 or AV1, which is what MKV files normally contain, so the video can often be copied across without re-encoding: fast, and with no loss at all.

MP4 also plays in far more places: every phone, browser, TV, editor, chat app and upload form.

MKV is a flexible container for any codec, with several audio and subtitle tracks; MP4 is the video container that plays on everything, usually holding H.264 video and AAC audio. Use MP4 whenever a video has to be sent, uploaded or played somewhere you don’t control.

MKV and MP4 compared
Property MKV MP4
Usually contains H.264 or HEVC video with AAC, AC-3 or Opus audio, often plus subtitles H.264 or HEVC video with AAC audio
Support Has patchy support Opens everywhere
Plays on VLC, Plex, Kodi and many smart TVs, but not iPhones, most editors or social apps Every phone, browser, TV, editor, chat app and upload form
Best for Films and series with several languages and subtitle tracks Sharing video anywhere
Introduced 2002 2003

How to convert MKV to MP4

  1. 01

    Add your MKV

    Drop your MKV video onto the box, or click to choose it. It is read from your disk and stays there.

  2. 02

    Check the settings

    The output is already set to MP4. Change the quality if you want to; the defaults suit most files.

  3. 03

    Save the MP4

    Press convert and save the MP4. Several files come back together as a ZIP.

What changes when MKV becomes MP4

Often a straight copy

When the MKV holds H.264, HEVC (H.265), VP9 or AV1 video, the stream is moved into the MP4 container untouched, so the conversion takes seconds even for long files. If the codec inside is something MP4 can’t hold, the picture is re-encoded instead and you’ll see a progress bar that takes longer.

Extra tracks

MKV files can hold several audio and subtitle tracks. The main video and first audio track are converted; use Unpack a Video to save the others as separate files.

The size stays about the same

MKV and MP4 are close in size for the same content, so do this for compatibility rather than to save space. MKV: Depends entirely on the codec inside. MP4: 1080p phone video runs roughly 60–130 MB a minute.

This page is put together from our notes on each format, choosing only what is true of MKV and MP4, so every pairing states the same facts the same way. How these pages are made.

Why it doesn’t upload

Video files are big, and uploading one just to change its container can take longer than the conversion itself. Your browser can read and write these formats, so the file never has to leave your device.

How to check for yourself

Worth knowing

  • About the MKV. Converting an MKV to a single-track format keeps only one audio track and drops soft subtitles unless you pick them.
  • About the MP4. An MP4 that won’t play is rarely broken; it usually holds a newer codec such as HEVC or AV1 that the player doesn’t support.
  • MP4, MOV, MKV and WebM are handled by your browser’s own video engine, often with hardware help. AVI, WMV, FLV, MPG and the other older formats use the FFmpeg engine, a one-time 31 MB download, and are slower.

Questions

Does converting MKV to MP4 lose quality?

Not when the video can be copied, which is the case for most MKV files: the stream moves into MP4 untouched. If it has to be re-encoded, the default quality keeps the difference invisible.

Will a MP4 play on my phone?

MP4 opens everywhere: every phone, browser, TV, editor, chat app and upload form. Every device plays MP4: double-click it, or drag it into a browser tab.

Read more about this

Other tools