MKV to MP4 Converter
Convert MKV videos to H.264 MP4 for phones, browsers and editors, in your browser. Free, private, no signup or upload.
About the MKV to MP4 Converter
This free MKV to MP4 converter repackages Matroska (.mkv) video into H.264 MP4, the format that plays natively on phones, browsers, editors and social platforms. MKV is a flexible container but many devices and apps do not support it; converting to MP4 makes your footage work everywhere.
The conversion runs in your browser through FFmpeg WebAssembly, so your video is never uploaded. The engine (about 30 MB) downloads from a CDN on first use and is cached, so the first conversion is the slow one. The output uses a web-friendly yuv420p pixel format and even dimensions for full device compatibility.
Converting re-encodes the video, so it takes some time and cannot exceed the quality of the MKV source — but a higher quality setting keeps more detail. Files up to 100 MB are supported.
How to Use the MKV to MP4 Converter
- 1Choose an MKV file, up to 100 MB.
- 2Pick a quality — Balanced is recommended.
- 3Click Convert to MP4 and wait for the progress bar.
- 4Preview the MP4 and download it.
Frequently Asked Questions
Is my file uploaded to a server?
No. All processing runs in your browser using FFmpeg compiled to WebAssembly. Your file never leaves your device — only the converter engine is downloaded, once.
Why is the first run slow?
The first time you use any converter here, the browser downloads the FFmpeg core (about 30 MB) from a CDN and compiles it. It is then cached for the session, so later runs are much faster.
Why won't my MKV play on my phone or browser?
MKV is not natively supported by many phones, browsers and social apps. Converting to MP4 with H.264 gives you a file that plays almost everywhere.
Will I lose quality?
At the High or Balanced setting the difference is very hard to notice. Converting cannot add quality, but a good setting preserves nearly all of the original detail.
Is there a file size limit?
Yes, 100 MB per file. Because everything runs in your browser's memory, very large files can be slow or run out of memory. Trim long clips first if you hit the limit.