01
Modern compression standards
MKV typically achieves better compression efficiency than WEBM at equivalent perceived quality. The result is a smaller file that still looks or sounds the same to most listeners and viewers.
100% local
VIDEO
Convert WEBM
to MKV
Modern compression standards.
MKV typically achieves better compression efficiency than WEBM at equivalent perceived quality. The result is a smaller file that still looks or sounds the same to most listeners and viewers.
— Drop area
WHY CONVERT
Why convert WEBM to MKV
02
Broader cross-platform support
MKV is accepted by a wider range of video players, mobile devices, and streaming platforms than WEBM. The conversion removes a recurring compatibility friction without changing what the file actually contains.
03
Lower storage and bandwidth cost
MKV files are typically smaller than their WEBM counterparts, which reduces hosting, transfer, and storage costs at scale. The savings compound when serving the same content to many recipients.
— How to convert
WEBM to MKV in three steps.
- 01
Open LocalConvert
Visit this page on any modern browser — no install, no signup, no plugin.
- 02
Drop or select your WEBM file
Drag your WEBM into the drop area, or click to pick one from your device.
- 03
Click Convert
Conversion runs entirely in your browser. When it's done, your MKV file downloads to your device.
QUALITY & FIDELITY
Quality and fidelity
- Lossy source to lossless target: existing artifacts are preserved but no new loss is added.
- Metadata (EXIF/tags) is preserved where the source provides it.
Transparency WEBM
✗ MKV
✗
Color depth 8/10-bit video, Opus/Vorbis audio any (container)
Metadata preserved ✓
FORMAT SPECS
Format specifications
| WEBM | MKV | |
|---|---|---|
| Extensions | .webm | .mkv .mka .mks |
| MIME types | video/webm | video/x-matroska |
| Introduced | 2010 | 2002 |
| Maintainer | Google / WebM Project | Matroska / CELLAR (IETF) |
| Magic # | 1A 45 DF A3 | 1A 45 DF A3 |
| Spec | View spec ↗ | View spec ↗ |
COMPATIBILITY
Where these formats work
| Platform | Windows | macOS | iOS | Android | Chrome | Firefox | Safari | Edge |
|---|---|---|---|---|---|---|---|---|
| WEBM | App | App | App | Native | Native | Native | Native | Native |
| MKV | Native | App | App | App | — | — | — | — |
WEBM
- Windows
- App
- macOS
- App
- iOS
- App
- Android
- Native
- Chrome
- Native
- Firefox
- Native
- Safari
- Native
- Edge
- Native
MKV
- Windows
- Native
- macOS
- App
- iOS
- App
- Android
- App
- Chrome
- —
- Firefox
- —
- Safari
- —
- Edge
- —
Why LocalConvert
How LocalConvert compares
| Category | LocalConvert | Cloud converters |
|---|---|---|
| PRIVACY | Files never leave your device. The whole pipeline runs in your browser via WebAssembly. | Files travel to a remote server, sit in queue storage, and may be retained for analytics or moderation. |
| COST | Free, no signup, no daily quotas. | Often free for small files; paid tiers for batch / large / commercial use. |
| LIMITS | Limited only by your device's memory and CPU. Multi-GB raw footage OK on desktop. | Typical 100 MB to 1 GB per-file caps, plus rate limits. |
— The formats
From · WEBM
Web Media
An open, royalty-free video container designed for the web. Often paired with VP9 or AV1 codecs.
Typical uses
Web video, screen recordings, HTML5 playback.
To · MKV
Matroska Video
An open, flexible container that can hold virtually any video, audio, and subtitle codec.
Typical uses
Movie archives, multi-language releases, home media.
— FAQ
Frequently asked.
Is WEBM to MKV conversion free?
Yes. LocalConvert is completely free, with no signup and no per-file or per-day limits.
Do my files get uploaded anywhere?
No. WEBM to MKV conversion happens entirely inside your browser using WebAssembly — your file never leaves your device.
What's the maximum file size?
There's no fixed cap — the practical limit is your device's available memory. Very large files may take longer or fail on low-RAM devices.
Does it work offline?
Yes — once the page has loaded, WEBM to MKV conversion works without an internet connection. Re-open the page once to cache it.
Will conversion preserve quality?
LocalConvert uses the industry-standard tools (FFmpeg, ImageMagick, Pandoc) — quality matches what professionals use on the command line. Lossy formats will still lose some quality on each re-encode.
— Related
Or convert these.
Browse all conversionsREFERENCES
Format references
Last verified:
100% local conversion.
WEBM to MKV is processed in your browser with WebAssembly. No upload, no tracking, no limits. Your file never leaves your device.