Remux, not convert
MKV and MP4 are containers — boxes for video, sound and subtitles. Changing the box (remuxing) copies the video bit for bit: no quality loss, and it runs as fast as your disk can read. Re-encoding is only needed when the video codec itself isn’t supported by your player.
What happens to each track
| In the MKV | In the MP4 |
|---|---|
| H.264 / HEVC video | copied as is |
| AAC, AC3, E-AC3 sound | copied (AC3 converted to AAC if your device needs it) |
| DTS, TrueHD, FLAC sound | converted to AAC — MP4 players rarely support them |
| Several audio languages | choose which to keep |
| Text subtitles (SRT/ASS) | saved as .srt next to the file, or burned in |
Why convert MKV at all?
iPhones, iPads, many TVs, PlayStation, video editors and web uploads accept MP4 but not MKV. If your TV plays the MKV picture without sound, the cause is the DTS or TrueHD track — fixing just the sound is enough.
MKV to MP4 for iPhone, iPad and Mac
Apple devices don’t open MKV at all, even when the video inside is ordinary H.264 or HEVC. After remuxing to MP4 the file plays in the Files app, Photos and QuickTime — and HEVC is tagged so that Apple players recognise it. Sound in DTS or TrueHD is converted to AAC because Apple devices can’t decode those formats.
MKV to MP4 for video editors and uploads
Premiere Pro, Final Cut Pro, iMovie and many web upload forms reject MKV. OBS records to MKV by default because a crash doesn’t corrupt the file; remux the recording to MP4 here before editing. Nothing is re-encoded, so the quality of your recording is untouched.
When remuxing isn’t enough
- VP9 or AV1 video — MP4 can hold it, but many TVs and editors can’t play it. Pick your device and the video is converted to H.264 only when needed.
- Image subtitles (PGS from Blu-ray, VobSub from DVD) — MP4 can’t carry them as text. They can be burned into the picture, which requires re-encoding.
- 10-bit HEVC — plays on modern TVs but not on older boxes and projectors; choose the device and it is converted to 8-bit when necessary.
Compared with VLC, HandBrake and online converters
VLC’s “Convert” re-encodes by default and is easy to get wrong; HandBrake always re-encodes, which takes many minutes per film and slightly lowers quality. Online converters upload multi-gigabyte files and usually cap them at 1 GB. Remuxing in the browser copies the video track as is, with no upload and no size limit.
Questions
Does MKV to MP4 lose quality?
Not when the video is copied: the picture is bit-for-bit identical. Only converted sound tracks are re-encoded, at high quality.
How long does it take?
Copying takes seconds to a minute per film. Converting DTS sound adds a few minutes because the browser decodes it with WebAssembly.
Can I convert a whole season?
Yes — drop the folder; files are processed in order and the folder structure is kept.
What if the MKV has VP9 or AV1 video?
MP4 can hold them, but many TVs can’t play them. Choose your device and the video is re-encoded to H.264 only if needed.
Does MKV to MP4 work on Mac?
Yes, in Chrome, Edge or Opera on macOS. The resulting MP4 plays in QuickTime, Photos and on iPhone and iPad.
Can I convert OBS recordings from MKV to MP4?
Yes. The video and audio are copied without re-encoding, so it takes seconds and the quality is identical.
Last updated: 2026-10-30