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MP4 to MKV - Online Video Converter
Convert MP4 to MKV online. Private, client-side - no uploadrequired. Batch conversion, quality presets, codec control.
Convert MP4 to MKV
Drop MP4 video here or click to select
MP4
MKV (H.264 / AAC)
About MP4 to MKV
Convert MP4 to MKV. MP4 pairs H.264 video with AAC audio in the ISO base media container. MKV is an open container holding multiple video, audio, and subtitle tracks. Only the selected tracks carry over, so pick audio and subtitles first..
Why convert MP4 to MKV?
- Smaller files with MKV lossy compression.
- Keep animation and transparency where supported.
- Private, no upload - runs in your browser.
MP4 vs MKV
| Animation | Yes | Yes |
|---|---|---|
| Transparency | No | Yes |
| Compression | lossy | lossy |
| Typical use | MP4 pairs H.264 video with AAC audio in the ISO base media container. | MKV is an open container holding multiple video, audio, and subtitle tracks. |
When not to convert MP4 to MKV
- Skip MKV for archival masters: lossy compression discards detail, so keep the MP4 original.
- Keep a master copy: repeated exports stack small losses, so archive MP4 before batch MKV shares.
Limits
Starting point: MP4 - H.264 video with AAC audio in one file. H.264 has no alpha channel, so transparency is dropped. Only the selected tracks carry over, so pick audio and subtitles first. Encode MKV (H.264 / AAC) from MP4 at a bitrate near the source, and confirm the audio track before converting.
How conversion works
Conversion runs entirely in your browser with FFmpeg WASM. Files never leave your device.
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FAQ
How do I convert MP4 to MKV?
Drop your MP4 file onto this page, choose quality and codec settings, then click Convert. The result downloads as MKV instantly. All processing runs in your browser.
What codec is used for MKV?
The default codec for MKV is H.264 / AAC. You can change the video and audio codec in Advanced mode.
How do you store my files?
We do not store any processed videos. All conversion happens entirely in your browser using FFmpeg WASM.