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WEBM MKV
File conversion

Convert WEBM to MKV

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Verified by Adam B.· reviewed by FE Editorial ·updated Aug 7, 2026
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Is it possible to convert WEBM to MKV?
Yes - WEBM converts to MKV.

You can do it right here with our free converter - no sign-up, and your file is deleted right after.

The fastest path is our free converter above or ffmpeg -i in.webm -c copy out.mkv on the command line. Because WebM is a constrained subset of the Matroska format, streams are simply repackaged - no quality is lost and file size barely changes.

Also to MKV: USM · TP · MPEG4

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Tested on macOS, Windows & Linux
Last verified Sep 2026

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WEBM → MKV converterFREE

Why convert WEBM to MKV?

People convert .webm to .MKV to unlock features WebM does not support: multiple audio tracks, chapters, and subtitle formats like SRT or SSA/ASS. MKV is also more widely accepted by desktop media players and video editors than WebM.

How to convert WEBM to MKV

MKVToolNix OPEN-SOURCE

Drag your .webm into MKVToolNix GUI, set the output path, and click Start multiplexing - no re-encoding occurs.

Freemake Video Converter FREE

Add your .webm, choose MKV as the output format, and click Convert.

Command line - ffmpeg CLI

Run ffmpeg -i in.webm -c copy out.mkv - the -c copy flag remuxes streams without touching video or audio.

Programs that convert WEBM

Miro Video Converter
Free Studio
Freemake Video Converter
MediaCoder
SUPER
Miro Video Converter for Mac

About these formats

.WEBM WebM Video

A WEBM file is Google's open video container that holds VP8, VP9 or AV1 video with Vorbis or Opus audio. Drag it into any modern browser or open it in VLC - no codec pack needed. If a…

Open .WEBM details →
.MKV Matroska Video

An MKV file is a Matroska multimedia container that holds video, multiple audio tracks, subtitles and chapters in one file. Open it for free with VLC media player, or on Windows 11 with the…

Open .MKV details →

Quality & what to watch

  • This is a remux, not a re-encode - video and audio are copied byte-for-byte, so there is no quality loss.
  • Codecs do not change: the output .mkv still contains VP8/VP9/AV1 video and Vorbis/Opus audio; only the container changes.
  • MKV is a desktop format - browsers cannot play it as a video source, so keep the original .webm if you need web embedding.

Frequently asked questions

Does converting WEBM to MKV reduce quality?
No - remuxing copies streams without decoding them, so quality is bit-for-bit identical to the source.
Why is the conversion so fast?
No decoding or re-encoding happens; only the container metadata is rewritten, so speed is limited by disk write speed, not CPU.
Will my media player support the output MKV?
Yes - MKV is widely supported by desktop players like VLC and mpv, and by most video editors.
Can I add subtitles or extra audio tracks during conversion?
Yes - in MKVToolNix drag in additional subtitle or audio files before multiplexing, and they all end up in one .mkv.