MP4 to MKV
Convert MP4 to MKV online, free — right in your browser. Nothing is uploaded.
Everything ran in your browser — nothing was uploaded.
How to use the MP4 to MKV
- Drop in your MP4 video.
- The output is already set to MKV.
- Click Process and download your MKV video.
About the MP4 to MKV
MP4 to MKV converts MP4 video into MKV, right in your browser. MP4 (H.264) is the universal video format — it plays on every phone, browser, TV, editor and social platform, which makes it the safe default for sharing. MKV is a flexible open container that can hold several audio and subtitle tracks — great for storing films, less so for sharing.
Converting MP4 to MKV gives you a flexible container that is handy for storing films with multiple tracks. The video is re-encoded to the target codec at high quality; converting cannot add quality the source never had, so start from the best original you have. Everything runs on your device with a WebAssembly build of ffmpeg, so your video is never uploaded — it is private, free and has no watermark. These tools are best for short clips, since the work runs on your device; the engine downloads once (about 25 MB) and is then cached.
Frequently asked questions
Is my video uploaded?
No. The conversion runs entirely in your browser with ffmpeg (WebAssembly). Your video never leaves your device.
Will converting MP4 to MKV lose quality?
The video is re-encoded to the target codec at high quality; converting cannot add quality the source never had, so start from the best original you have.
Why is it slow on long videos?
The work happens on your own device rather than a server, so long or high-resolution clips are demanding. Trim first or use a shorter clip for best results.
Is there a watermark or sign-up?
No. It is completely free, needs no account, and never adds a watermark.