WEBM to MKV
Re-encode WEBM video to MKV in your browser. Everything runs on your device, so even large files never leave it.
From
WEBM (.webm)
To
MKV (.mkv)
Advanced options
Files whose codec MKV already supports are repackaged losslessly and ignore both settings.
- When the source already uses a codec the target container supports, the file is repackaged rather than re-encoded — that is near-instant and completely lossless.
- Otherwise the video is re-encoded using your device's hardware encoder. Large files can take several minutes, so keep this tab open.
- Conversion uses the audio and video codecs built into your browser, so results depend on your device. Unsupported targets are greyed out.
Drop WEBM files here, or use the button below
Converted on your device — your files are never uploaded.
About these formats
- WEBM — WebM video
- Open, royalty-free web video — smaller files than MP4.
- MKV — Matroska video
- Flexible container favoured by archives — holds almost any codec.
- When the source already uses a codec the target container supports, the file is repackaged rather than re-encoded — that is near-instant and completely lossless.
- Otherwise the video is re-encoded using your device's hardware encoder. Large files can take several minutes, so keep this tab open.
- Conversion uses the audio and video codecs built into your browser, so results depend on your device. Unsupported targets are greyed out.
Other WEBM conversions
Private by design — no upload, no sign-up
This WEBM to MKV converter runs locally, using your own browser. Your files are never uploaded to a server, so they stay on your device from start to finish.
- Are my WEBM files uploaded to a server?
- No. The WEBM to MKV conversion runs locally in your browser using your own device's CPU. Your files are never uploaded, never transmitted over the network and never stored on a server.
- Is there a file size limit for WEBM to MKV?
- There is no imposed limit, because nothing is uploaded. The practical ceiling is your device's available memory, so very large files may be slower on older hardware.
- Does it work offline?
- Yes. Once the page has loaded, converting WEBM to MKV keeps working without a network connection, since the conversion happens entirely on your device.
- Do I need to sign up or install anything?
- No. There is no sign-up, no account and no software to install. Pick a WEBM file and convert it to MKV straight away.
- Is converting WEBM to MKV free?
- Yes, it is free to use, with no watermarks and no daily quota.