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MKV to WebM Converter

Convert MKV files to WebM without installing software or uploading anything. If your MKV contains VP9 video, Smart mode copies it into the WebM in seconds; other codecs are re-encoded to VP8.

  • Free, no sign-up
  • Files never leave your device
  • Powered by FFmpeg
  • No watermark
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Your files are processed on this device and are never uploaded to a server.

What happens when you convert MKV to WebM

Inside a typical MKVH.264, HEVC (H.265) or VP9 video with AAC, AC-3 or Opus audio
Copy without re-encodingSometimes: it depends on the codec inside your file, and Smart mode checks this automatically
When re-encodedVP8 video with Vorbis audio
Extra tracksOnly the first video and audio track are kept; extra audio tracks and subtitles are dropped
Opens inall current browsers and VLC; iPhone apps, PowerPoint and many editors do not

Sizes are typical values; your files will vary with content and settings.

MKV

MKV Matroska Video

MKV is an open container that can hold almost any codec plus multiple audio tracks and subtitles. It is popular for archived films and series.

MKV converter
WebM

WebM WebM Video

WebM is an open, royalty-free container built for the web, usually holding VP8 or VP9 video with Opus or Vorbis audio. Browser screen recorders and many web apps save WebM by default.

WebM converter

How to use the MKV to WebM Converter

  1. 1

    Choose a MKV file or drop it onto the page.

  2. 2

    Review the video options. The defaults suit most files.

  3. 3

    Click Convert and download your WebM when processing finishes.

Why convert MKV to WebM?

MKV is common for films, TV episodes and OBS recordings, because one file can hold several audio and subtitle tracks. iPhones, browsers and most social networks will not play MKV files. Choose WebM to embed video on a website using open, royalty-free codecs.

Frequently asked questions

Will the WebM lose quality?

Both formats are lossy, so converting re-encodes the data once more. Using a high quality setting keeps the generational loss very small. Avoid converting the same file back and forth repeatedly.

Does converting MKV to WebM re-encode the video?

Sometimes: it depends on the codec inside your file, and Smart mode checks this automatically. A typical MKV contains H.264, HEVC (H.265) or VP9 video with AAC, AC-3 or Opus audio. Otherwise the result is VP8 with Vorbis audio.

Questions about privacy, file-size limits or conversion speed are answered in the general FAQ.