Convert MKV to MP4 online
Convert a MKV file to MP4 directly in your browser — the file is never uploaded to a server.
or click to select it
Convert an MKV video (the go-to format for downloaded or ripped movies and TV shows, able to hold multiple audio tracks, subtitle tracks and various codecs at once) to MP4 with H.264 and AAC, the combination that plays on virtually every phone, smart TV, game console and social platform, directly in your browser.
Matroska (MKV) is a very flexible container that can wrap almost any video or audio codec, plus multiple subtitle and audio tracks at once — exactly what makes it so popular for downloads, but also what keeps many devices from playing it natively. The tool re-encodes the video and audio to H.264/AAC inside an MP4, the format with the broadest guaranteed compatibility.
Use cases
- Convert a downloaded movie or episode in MKV so it plays on a phone, smart TV or game console that doesn't support MKV natively.
- Prepare an MKV video for uploading to a social platform or site that only accepts MP4.
- Share an MKV file with someone whose player doesn't recognize it.
How it works
- 1
Upload your MKV video
Drop the file in or select it from your device.
- 2
Click Convert
ffmpeg.wasm re-encodes the video to MP4 (H.264 + AAC) in your browser.
- 3
Download the MP4
Once it's done, download the converted video.
Technical details
Runs ffmpeg.wasm inside a Web Worker in your browser. Unlike a simple container swap, every frame gets re-encoded here, so the process can take several minutes depending on file size. If the source MKV has multiple audio tracks or embedded subtitles, the output keeps only the first video and audio track — subtitles aren't carried over into the final MP4.
Frequently asked questions
Why won't my TV or phone play MKV files?
Many devices only have licensing or hardware support to decode certain codecs inside MP4 (typically H.264/AAC), even though MKV can hold those exact codecs or others the device doesn't understand.
What happens to the subtitles or extra audio tracks in my MKV?
Only the first video and audio track from the original file are kept; subtitle tracks and any additional audio tracks aren't included in the resulting MP4.