01
Add your WEBM
Drop the file on the panel, choose it from disk, or open it from Your Library. Wait until the name and length appear.
WEBM to MKV
Turn browser WEBM files into Matroska MKV for flexible desktop playback and local archives — right in your browser.
Drop a WEBM file here
or click to choose from your computer
WEBM · VP8 · VP9 · browser recordings
Your file will be converted to MKV. Click Convert when ready.
Converting…
Local processing in your browser · Files are not uploaded to our servers
About WEBM to MKV conversion
WEBM is a web-oriented container. MKV (Matroska) is a flexible open container popular for desktop libraries and backups. Converting WEBM to MKV helps when you want browser captures stored alongside other desktop video in one player-friendly format.
Sound Booster converts in the browser: add a WEBM, encode to MKV, then download or save to Your Library. Everyday files are meant to stay on your device for this step.
Choose WEBM to MKV for local archives, VLC-style playback, and folders where you mix screen recordings with other downloads. For social uploads and many mobile apps, MP4 is still the safer target — use the WEBM to MP4 page when that is the goal.
Large recordings need enough free memory in the tab. If encoding stalls, try a shorter clip first. The progress bar shows approximate percentage while the browser works so you know the job has not frozen.
How to convert WEBM to MKV
02
Convert to MKV
Click Convert to MKV and keep the tab open while the browser encodes. The first run may load a small local encoder.
03
Download or save
Save the MKV file to your device, or store it in Your Library for later tools on Sound Booster.
WEBM and MKV formats
What is a WEBM file?
WEBM is a media container built for the web. Browsers often record or export video as WEBM (for example Chrome screen capture). It typically uses open codecs and plays well in HTML5 players, but many phones, editors, and upload forms still prefer other containers.
What is an MKV file?
MKV (Matroska) is an open container that can hold video, audio, and subtitles. Desktop players such as VLC handle it well. It is a common choice for local libraries when you want flexibility beyond a single commercial upload format.
What people use it for
Desktop media libraries
Store browser WEBM clips as MKV next to other downloads in a single desktop-friendly library.
Playback outside the browser
Open converted files in cross-platform desktop players when you no longer need a web-only container.
Backup of web captures
Normalize a folder of WEBM recordings into MKV for long-term storage on a PC or external drive.
When MP4 is not required
Use MKV for local archives where a website does not force MP4, but you still want something more flexible than WEBM alone.
Frequently asked questions
Should I pick MKV or MP4 from WEBM?
MP4 is the safer choice for phones, social uploads, web forms and most video editors, because almost every device and platform accepts it. MKV is better for desktop libraries, local backups and players such as VLC, where you want a flexible container. Decide by the destination: if a website or app is next, pick MP4; if the file will sit on your own drive, MKV is a good fit.
Do my files leave this device?
No. Conversion is designed to run in your browser, so the WEBM is read from your device and the MKV is written back to your device. Nothing has to be sent to Sound Booster servers for this step, which matters for private screen recordings, meeting captures and unpublished clips. On the first run the page may load a small local encoder, but your video is not part of that.
Will phones play MKV?
Support varies by device. Many phones and tablets cannot open MKV in their default gallery or video app, even though desktop players handle it easily. If you plan to watch or share the clip on a phone, convert WEBM to MP4 instead, or install a third-party player that understands Matroska files.
Is WEBM to MKV free?
Yes. The converter is free and does not ask you to create an account. You can convert one file after another; the practical limit is how much memory your browser tab has for a large recording, not a paywall or a daily quota.
Why did conversion fail?
The most common cause is a large recording and not enough free memory in the tab. Try a shorter clip, close other heavy tabs, and keep the converter tab open and in the foreground until the progress bar finishes. If a file still fails, it may be damaged or recorded with unusual settings: play it once in your browser to confirm it opens, or record it again.
What is the difference between a WEBM and an MKV file?
Both are containers, not codecs, and WebM is actually built on the Matroska structure that MKV uses. WebM is a stricter profile meant for the web and typically carries VP8 or VP9 video with Vorbis or Opus audio. MKV is the more general format: it accepts more codecs, plus chapters, extra audio tracks and subtitles, which is why desktop archives like it.
Will converting WEBM to MKV reduce video quality?
The goal is to keep picture and sound as close to the original as possible, because you are changing the container rather than editing the content. Since encoding happens inside your browser, it is still worth checking a short test clip first. If you only need a quick preview of the result, convert a few seconds and compare it with the original in a desktop player.
Can I convert a screen recording made in Chrome?
Yes, this is one of the most common uses. Chrome screen capture and many browser-based recorders save WEBM files by default, and those play fine in a browser but are awkward in some editors and media libraries. Drop the recording on the panel, convert it to MKV, and keep it next to your other desktop video files.
Can an MKV file hold subtitles and several audio tracks?
The MKV format can store multiple audio tracks, subtitle streams, chapters and attachments in one file. This converter focuses on turning your single WEBM into an MKV, so it does not add subtitle tracks or merge extra audio for you. If you need those, add them afterwards with a desktop tool that edits Matroska files.
Can I convert several WEBM files at once?
The converter works on one file at a time: add a WEBM, convert it, download the MKV, then load the next one. Keeping it to a single file also keeps memory use predictable in the browser tab. For a whole folder of recordings, repeat the steps for each file, or save finished files to Your Library to keep track of them.