About this tool
OBS and many capture tools record to MKV because it survives crashes, but editors, phones, and upload forms want MP4. Since MKV usually contains H.264 video and AAC audio, this converter copies the streams into an MP4 container in seconds, with no quality change.
About the formats: MKV (Matroska) is a flexible open container popular with OBS recordings and high-quality rips. It can hold almost any codec plus multiple audio and subtitle tracks, but phones, smart TVs, and web players usually reject it. MP4 is the universal video container, usually holding H.264 video and AAC audio. It plays on every phone, browser, TV, and editing program, which is why most platforms ask for it.
MKV and MP4, side by side
| .mkv in | .mp4 out | |
|---|---|---|
| Usual codecs | Anything | H.264 video, AAC audio |
| Plays on | VLC, mpv, some TVs | Everything |
| Subtitles | Yes, many tracks | Limited |
| Best for | Archiving, rips | Sharing and uploading |
Rows where the two differ are marked. The full story on each: MKV files and MP4 files.
How to use it
- Drop your MKV files into the box above, or click to browse. Nothing is uploaded.
- Adjust the options if you want; the defaults suit most files.
- Click Convert to MP4 and wait a moment.
- Download the results individually or all at once as a ZIP.
Questions
Are subtitles kept?
No. Subtitle tracks are dropped because MP4 players handle them inconsistently; video and the first audio track are preserved.
What if my MKV has multiple audio tracks?
The first audio track is used.
Why does re-encoding take so long?
Encoding video in the browser runs on a single CPU core, so a re-encode processes roughly real time or slower for 1080p footage. Container swaps (stream copy) are near instant. Keep clips short or lower the resolution when you need speed.
Is it free, are files uploaded, which browsers work: the general questions are answered once for the whole site.