Convert MKV to WebM Online
Turn MKV files into WebM directly in your browser using ConverterUp. There is no upload, no waiting in a queue, and no account required — your files stay on your device while WebAssembly does the work locally. Adjust quality and dimensions where supported, then download the result. The output keeps the visual fidelity you'd expect from a desktop app while running entirely in the browser tab.
Convert MKV to WebM nowHow to convert MKV to WebM
Open the converter
Click the button to open the MKV to WebM tool. It loads instantly — no install, no signup.
Drop your MKV file
Drag your MKV file into the upload area or click to browse. The file stays in your browser memory only.
Download WebM
The conversion runs locally and finishes in seconds. Click download to save the WebM file to your device.
MKV vs WebM at a glance
Key technical differences between the two formats, so you know what to expect before converting.
| Feature | MKV | WebM |
|---|---|---|
| Type | Video container | Video container |
| Compression | — | Lossy |
| Audio track | Yes | Yes |
| Common codecs | H.264, HEVC, VP9, AV1, AAC, Opus, FLAC | VP8, VP9, AV1, Vorbis, Opus |
| Browser support | Partial | All modern browsers |
| Extensions | .mkv | .webm |
| MIME type | video/x-matroska | video/webm |
| Introduced | 2002 · Matroska | 2010 · Google |
What changes when you convert MKV to WebM
- MKV and WebM are containers. The video and audio streams are re-encoded into codecs that WebM supports (typically VP8, VP9, AV1), so you get a file that plays reliably rather than a simple rename.
- The audio track is carried over to the WebM file, re-encoded if needed.
- Compatibility improves: WebM opens in more browsers, apps and operating systems than MKV.
About MKV
MKV (Matroska) is an open container that can hold almost any video, audio and subtitle codec, with multiple audio tracks, chapters and subtitles in one file.
- Best for
- Movie and TV rips, multi-language videos, archiving with subtitles.
- Strengths
- Extremely flexible, open standard, keeps multiple tracks and subtitles.
- Limitations
- Not playable in Safari or on many phones and TVs without extra apps.
About WebM
WebM is an open, royalty-free video container from Google based on Matroska. It carries VP8, VP9 or AV1 video with Vorbis or Opus audio and is designed for HTML5 video.
- Best for
- Video on websites, screen recordings from browsers and open-source workflows.
- Strengths
- Royalty-free, efficient VP9/AV1 compression, native in modern browsers.
- Limitations
- Less accepted by editing software, older Apple devices and some social platforms.
Frequently asked questions
Is the MKV to WebM conversion really free?
Yes. ConverterUp is fully free, with no signup, no watermarks, and no daily quota for the MKV to WebM converter. We support the project through unobtrusive ads.
Are my MKV files uploaded to a server?
No. Conversion runs in your browser using WebAssembly. The MKV bytes never leave your device, and we have no upload endpoint at all.
What is the maximum file size?
For MKV input, the soft cap is 50 MB for images and 500 MB for video. Practical performance depends on your device's RAM.
Will the WebM file open everywhere?
In all current browsers and most up-to-date apps, yes. Some older software and devices may still not open WebM files.
Does converting MKV to WebM keep the sound?
Yes. The audio track is kept and, if necessary, re-encoded into a codec that WebM supports.
Related guide
PNG vs JPG vs WebP: Which Format to Use WhenRelated conversions
Ready to convert MKV to WebM?
Open the tool, drop your file, and download the result. No upload, no signup, no watermarks.
- 100% private
- No upload
- No signup
- Free forever