MKV to WebM Converter
Turn an MKV into a WebM for web pages and HTML5 players. Free, no signup, no watermark.
MKV to WebM Converter Features
EchoWave is used by creators, marketers, educators, and businesses to convert and edit media online.
To convert MKV to WebM, upload the MKV and download a WebM with VP9 video and Opus sound, the open pair every major browser plays in a video tag. If the MKV already holds VP9 or AV1 with Opus audio, choose Copy source stream under advanced settings to rewrap it without re-encoding. Free, with no signup and no watermark.
How it works
How to convert MKV to WebM
- 1
Upload your MKV
Drop the MKV on this page or pick it from your phone or computer. No account and nothing to install.
- 2
Convert to WebM
WebM is already selected. Start, and you get VP9 video with Opus sound. Advanced settings change the codec.
- 3
Download the file
Save the WebM. Need a trim or a resize first? Open it in the editor.
Try it
Estimate your WebM
A video's size is its bitrate times its length. Pick a bitrate and a length for a rough guide.
Drag to set the clip length in minutes, from 1 to 30.
A guide only: the converter sets the quality for you, and a straight rewrap keeps the source size.
The formats
MKV vs WebM
Matroska Video
An open container that holds almost anything
- Type
- Open video container
- Holds
- Almost any codec, plus several audio and subtitle tracks
- File size
- Depends on the codec inside, not the container
- Plays on
- VLC and media servers, less on phones and TVs
Best for:Movies with several audio tracks and subtitles
WebM
Open video built for the web
- Type
- Open web video container
- Holds
- VP8, VP9, or AV1 video with Opus or Vorbis audio
- File size
- Small for its quality
- Plays on
- Chrome, Firefox, Edge, Android, recent Safari
Best for:Video embedded on web pages
What changes from MKV to WebM
- The video is re-encoded to VP9 and the sound to Opus, the standard pair for WebM. A re-encode compresses the picture again, so the result is at best as sharp as the MKV.
- Only the main video and one audio track are kept. Extra audio languages, subtitle tracks, and chapters are not copied, so keep the original if you need them.
- Advanced settings let you pick the codec yourself: VP8 or AV1, or Copy source stream to rewrap without re-encoding when WebM accepts what is inside.
Use cases
What people use it for
Troubleshooting
If something looks off
The WebM will not play
The file got bigger
My subtitles or second language are missing
FAQ
MKV to WebM questions
How do I convert MKV to WebM?
Can I convert MKV to WebM without re-encoding?
Will the WebM be smaller than the MKV?
What happens to subtitles and extra audio tracks?
Will the WebM play on iPhone?
Is the MKV to WebM converter free?
When to choose WebM over MP4 for an MKV
WebM is the open web video format: VP9 or AV1 video with Opus sound, played natively by Chrome, Firefox, Edge, and recent Safari. It suits a video you host on your own page, where smaller files load faster and no licensing questions come up.
For anything people download, share in messages, or open on a TV, MP4 is still the safer target, and MKV to MP4 rewraps plain H.264 MKVs without re-encoding. Already have an MP4? MP4 to WebM does the same job from there, and the MKV converter lists every other output.
What people say after converting with EchoWave
About the EchoWave team
EchoWave is a browser-based video and audio editor built by Lemon Vault LLC since 2018. The people who build the editor write these guides and test every step in the production app before publishing.
Convert MKV to WebM for free Free online converter
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