MP4 to MKV without re-encoding
This MP4 to MKV converter moves the contents of MP4 files into Matroska (.mkv) containers inside your browser. Matroska accepts virtually every codec, so the video and every audio track are copied across exactly as they are — no re-encoding, no change in quality, and only seconds of work even for a long film.
People switch to MKV to standardise a media library, to feed a collection that a media server such as Plex, Jellyfin or Kodi organises, or to use Matroska tools such as mkvmerge to add subtitle and audio tracks later. The conversion is private: files are read from your disk and written on your own device.
How to use the MP4 to MKV Converter
- Drop MP4 or M4V files on the upload area.
- Check the plan — normally every row says Copy. Extra audio tracks appear on their own lines with their language.
- Leave the codecs on “Keep original” for a pure remux. Pick a codec or a resolution only if you really want the video re-encoded, for example to AV1 for a smaller archive copy.
- Press Convert to MKV and download the result, or the whole batch as a ZIP.
MP4 to MKV Converter features
Pure remux
H.264, HEVC, AV1, VP9, AAC, Opus, MP3, AC-3 and more are all valid in Matroska, so they are copied bit for bit.
All tracks, with languages
Multiple audio tracks keep their order and language tags — useful for dubbed films and commentaries.
Optional re-encode
Convert to AV1, HEVC or VP9 in the same step if you want a smaller archive.
Tags carried over
Title, date and comment tags move into Matroska’s own tag fields.
No install, no upload
Works in a browser tab on Windows, macOS, Linux or ChromeOS.
What Matroska is
Matroska began in 2002 as an open, royalty-free container format, named after the Russian nesting dolls. It stores everything in EBML, a binary cousin of XML, so new codecs and features can be added without breaking older players. In 2024 the format was published by the IETF as RFC 9559, and WebM is a restricted subset of it.
MKV’s strengths are flexibility and features: any number of video, audio and subtitle tracks, chapters, attachments such as the fonts that styled subtitles need, and almost any codec. That is why film collectors and media-server users favour it.
MP4 or MKV: which should you keep?
In short: MKV for storing and watching on computers and media players, MP4 for sharing and editing. MKV to MP4 takes you back just as quickly.
| MP4 | MKV | |
|---|---|---|
| Standard | ISO/IEC 14496-14 | IETF RFC 9559, royalty-free |
| Codecs | A defined set; best support for H.264, HEVC and AAC | Almost anything, including FLAC, DTS and PCM |
| Subtitles | Limited timed-text formats | SRT, ASS/SSA, PGS, VobSub and more |
| Chapters and attachments | Basic | Full support |
| iPhone, iPad, QuickTime | Yes | No |
| Android, VLC, Kodi, Plex | Yes | Yes |
| Editing apps and social media | Widely accepted | Often rejected |
Good to know
- Phone videos with a rotation flag (most portrait clips) are re-encoded upright, because Matroska has no standard rotation field. The plan says so before you convert.
- Subtitle tracks inside the MP4 aren’t copied by the browser engine; the plan lists them. Save them with Extract Subtitles and add them to the MKV with any Matroska tool.
- Timecode and camera-data tracks are left out; they matter only in professional editing.
- To shrink the finished file, the MKV compressor re-encodes it to a size you choose.
MP4 to MKV Converter FAQ
How do I convert MP4 to MKV?
Drop the MP4 files above and press Convert to MKV. Because Matroska accepts the codecs MP4 uses, the streams are copied and the MKV is ready almost immediately.
Does MP4 to MKV lose quality?
No. With “Keep original” selected nothing is decoded or compressed again; the MKV contains the same video and audio data as the MP4.
Why is my MKV a slightly different size?
Only the container overhead changes. Matroska and MP4 index the data differently, so the files differ by a few kilobytes up to a few megabytes.
Will the MKV play on my TV?
Most smart TVs, streaming sticks and media players play MKV with H.264 or HEVC video. iPhones and Apple TV’s own player don’t; a player app such as VLC handles it there.
Why does a portrait video get re-encoded?
Phones store portrait video as landscape frames plus a “rotate 90°” flag. MP4 has a place for that flag and Matroska doesn’t, so the frames are turned upright and encoded again to display correctly.
Is it safe and free?
Yes. The conversion runs on your device with Mediabunny (MPL-2.0) and your browser’s media APIs — no uploads, no watermark, no limits.