MKV to MP4 Converter (Free, Online, No Upload)

Convert any MKV file to MP4 right in your browser. Nothing gets uploaded to a server. MKV files often contain H.264 or H.265 video that can be remuxed to MP4 without re-encoding for a near-instant conversion. The conversion runs locally using FFmpeg compiled for your browser, so your files stay on your device.

Try it in your browser

Loading FFmpeg engine... (~31 MB)

Use the API

curl -X POST https://renderio.dev/api/v1/run-ffmpeg-command \
  -H "X-API-KEY: ffsk_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{
  "ffmpeg_command": "-i {in_video} -c copy -movflags +faststart {out_video}",
  "input_files": {
    "in_video": "https://example.com/input.mkv"
  },
  "output_files": {
    "out_video": "output.mp4"
  }
}'

Need an API key? Get your free API key to start processing files programmatically.

Common Variations

Re-encode video and audio

-i input.mkv -c:v libx264 -crf 23 -c:a aac -movflags +faststart output.mp4

Copy video, re-encode audio only

-i input.mkv -c:v copy -c:a aac -movflags +faststart output.mp4

Select specific streams

-i input.mkv -map 0:v:0 -map 0:a:0 -c copy -movflags +faststart output.mp4

With subtitle burn-in

-i input.mkv -vf subtitles=input.mkv -c:v libx264 -crf 23 -c:a aac output.mp4

Related Operations

Free MP4 to WebM Converter Online | RenderIO Free AVI to MP4 Converter Online | RenderIO Convert MOV to MP4 Online Free, No Upload | RenderIO Add Subtitles to Video Online Free, No Upload | RenderIO

Need to process at scale?

Automate this with the RenderIO FFmpeg API. Process thousands of files programmatically or through no-code video automation.

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