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MKV
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WEBM

MKV to WebM Converter — Free, Online, No Upload

Publish MKV videos on the web without a CDN or video host — WebM plays natively in every browser.

Free · no signup2 free files a day100% in-browser · no upload

Tap to select MKV files

or click to browse

2 free files per day (2 left today) · Up to 10 MB each · Upgrade for more

✓ Files never uploaded✓ 100% browser-based✓ No account required
Need the reverse?WEBM → MKV

How to convert MKV to WEBM online

  1. 1

    Drop your MKV file

    Drag your Matroska Video file onto the box above, or click it to pick a file.

  2. 2

    Wait a few seconds

    Conversion starts on its own and runs on your device, not on a server.

  3. 3

    Download your WEBM

    Click Download to save the WebM Video Format file.

MKV vs WEBM: format overview

MKV

Matroska Video

Matroska.org · 2002

Compression
lossy
Transparency
No
  • ✓ Supports virtually any codec combination
  • ✓ Multiple audio tracks and subtitles per file
  • ✗ Not natively supported by iOS or older devices
WEBM

WebM Video Format

Google (On2 Technologies) · 2010

Compression
lossy
Transparency
No
  • ✓ Royalty-free codec (VP8/VP9/AV1)
  • ✓ Excellent web streaming support

MKV magic bytes: 1A 45 DF A3

WEBM magic bytes: 1A 45 DF A3

Why convert MKV to WEBM?

MKV is a desktop media format — at home on a media server, a TV stick, or a computer running VLC, but completely absent from the HTML5 video ecosystem. Browsers cannot play MKV in the HTML5 video element. If you want to publish video content from your media library on a website, a web app, or an online platform, MKV files must be converted to something browsers actually support.

WebM is the browser-native open video format. Chrome, Firefox, and Edge all play WebM natively with no plugins. It holds VP8, VP9 or AV1 video and Opus audio, all royalty-free. This converter writes VP8 with Opus sound, which plays in every current browser but is usually larger than an H.264 file of the same clip.

Converting MKV to WebM transcodes the video to VP8 and the audio to Opus. MKV files often carry high-resolution H.264 or H.265 video, which has to be re-encoded for WebM. The output WebM file is compact, open-format, and embeds directly in an HTML5 video element. MKV files with several audio tracks keep the one with the most channels. Note that Safari support for WebM is improving but not universal — serving an MP4 fallback alongside WebM ensures coverage across all browsers.

Quality & file size: MKV to WEBM

Typical sizes (1 minute 1080p): MKV 200–800 MB → WEBM 50–200 MB.

Frequently asked questions

Can I self-host WebM video on my website instead of using YouTube?
Yes — WebM is specifically designed for HTML5 web video. Self-host the file on your server, link it in a <video> element, and it plays in Chrome, Firefox, Edge, and modern Safari without plugins.
Will subtitles from my MKV transfer to WebM?
WebM supports WebVTT subtitles embedded in the container. SRT or ASS/SSA subtitles from MKV may need conversion. Our converter transfers the video and audio tracks; subtitle handling depends on the subtitle format.

Your MKV file never leaves this tab — FormatDrop has no endpoint that receives file data. How it works