Convert MKV to WebM
Free MKV to WebM converter that runs entirely in your browser. No uploads, no signup required.
Drop MKV files here
or browse your device. Free, no signup required, no watermarks.
Files are processed on your device, never uploaded
Media conversions run on a full FFmpeg engine compiled to WebAssembly. The engine (~31 MB) downloads once on your first conversion, then everything runs locally.
Three steps
How to convert MKV to WebM
Add your files
Drop MKV files into the box above, or click it to browse. Add several to batch convert.
Convert
WebM is already selected as the output. Hit Convert. Your browser does the work locally.
Download
Save each converted WebM file. Pro ZIPs whole batches in one click.
Matroska video
MKV
MKV is an open container that can hold any codec, multiple audio tracks, and subtitles in one file.
WebM video
WebM
WebM is the open web video format built for browsers, with strong compression and no licensing fees.
Why convert MKV to WebM?
MKV is an open container that can hold any codec, multiple audio tracks, and subtitles in one file. WebM is the open web video format built for browsers, with strong compression and no licensing fees. Converting from MKV to WebM gets you the best of the target format wherever MKV falls short, whether that's compatibility, file size, or what your apps and devices can open. With FormatFusion the switch takes seconds and your files stay on your device the whole time.
Questions
MKV to WebM: common questions
Is this MKV to WebM converter free?
Yes. It is completely free with no watermarks and no account required, for files up to 1 GB each. Convert one file or a hundred.
Is it safe to convert MKV files here?
Safer than any upload-based converter. The conversion runs locally in your browser, so your MKV files are never sent over the internet and never touch a server.
Will I lose quality converting MKV to WebM?
No. This conversion preserves your content, and WebM output keeps everything the format supports.
Can I convert multiple MKV files at once?
Yes. Free converts up to three MKV files at a time. FormatFusion Pro batches without limits and downloads whole runs as a single ZIP.
Does it work on iPhone and Android?
Yes. FormatFusion runs in any modern mobile or desktop browser. No app install needed.