MKV to MP4 converter
This MKV to MP4 converter makes a video playable on TVs, iPhones and in editing software. Picture and sound are usually repackaged unchanged into an MP4 container, which takes seconds and costs no quality. The file stays in your browser and is never uploaded.
Source: MDN – Media container formats: Matroska (MKV) and MP4 as containers for multiple video and audio tracks. Updated: .
How it is calculated
Why convert MKV to MP4?
MKV is the Matroska container: a free, very flexible format that can hold several audio tracks, subtitles and chapters. Many devices still do not know it – TVs, iPhones, the Windows Explorer preview and many editing programs expect MP4. Conveniently, an MKV file often contains the same H.264 video that fits into an MP4 file, so nothing has to be recalculated. This tool copies picture and sound bit for bit into an MP4 container (remuxing). For a film that takes seconds to minutes and the quality stays exactly the same.
When is re-encoding needed?
| Situation | Recommendation |
|---|---|
| Picture is H.264 (typical) | Copy unchanged – fast, no loss |
| Picture is HEVC/H.265 or AV1 and the device is older | Re-encode as H.264 – plays almost everywhere, takes longer |
| Sound is AAC, MP3, Opus, FLAC or AC-3 | Carried over |
| Sound is DTS or TrueHD | The browser cannot read it – the sound is missing and a notice says so |
What does not come along
- Subtitles and chapters are not carried into the MP4 file; subtitles burned into the picture stay visible, of course.
- Very large films: the result is held in memory. Files up to 4 GB are allowed, but multi-gigabyte rips fail on weak devices. Short clips, episodes and recordings work fine.
- If the file has several video tracks, the main one is used.
Privacy
The video is only read piece by piece from your device; there is no upload. The open-source library Mediabunny (MPL-2.0) reads and writes the containers. Afterwards you can shorten the MP4 with Trim video, shrink it with Compress video or mute it with Remove audio from video.
Frequently asked questions
How do I convert MKV to MP4?
Choose the MKV file and click “Convert MKV to MP4”. The tool repackages picture and sound into an MP4 container and offers the result for download. Nothing is uploaded.
Is quality lost when converting MKV to MP4?
Not in the default mode: picture and sound are copied without re-encoding. Only if you choose “Re-encode as H.264” is the picture recalculated.
Why is the sound missing after conversion?
The sound was probably encoded as DTS or TrueHD. The browser cannot read those formats, and the tool shows a notice. A desktop program such as HandBrake can convert them.
What happens to subtitles and multiple audio tracks?
All audio tracks that fit into MP4 are carried over. Subtitle tracks and chapters are not.
How long does the conversion take?
Remuxing usually takes a few seconds to minutes because nothing is recalculated. Re-encoding takes longer, roughly as long as the video depending on your device.
Can I convert a whole movie?
Up to 4 GB file size, yes, as long as your device has enough memory, because the finished MP4 is built in memory. For very large film files a desktop program is the better choice.
Sources and legal basis
- MDN – Media container formats: Matroska (MKV) and MP4 as containers for multiple video and audio tracks
- Matroska.org – Basics: Matroska als Container-Format (EBML, RFC 8794)
- MDN – Web video codec guide: H.264 (AVC), HEVC (H.265), AV1 in MP4
- MDN – VideoEncoder.configure(): bitrate in Bit pro Sekunde
- MDN – EncodedVideoChunk.type (key/delta)
- ITU-T H.264 – Advanced video coding for generic audiovisual services
- Mediabunny 1.61.0 – Vanilagy (MPL-2.0), Quelltext
- Licenses of the media tools (MPL-2.0)
As of: · Editorial policy
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