Convert WebM Video (.webm) to Matroska Video (.mkv) online for free. Fast, secure video conversion with no watermarks or registration.
Conversion settings — add a file to adjust
Upload your .webm file by dragging it into the upload area or clicking to browse.
Choose your output settings. The default settings work great for most files.
Click Convert and download your .mkv file when it's ready.
WebM and MKV are closely related — WebM is a restricted subset of the Matroska (MKV) container format, limited to VP8/VP9/AV1 video with Vorbis/Opus audio. MKV supports any codec combination, including H.264, H.265, DTS, AC3, and unlimited subtitle tracks. Converting WebM to MKV lifts these restrictions while maintaining the Matroska container's capabilities.
MKV's broader codec support enables adding audio tracks in formats WebM does not support (AC3, DTS, FLAC), embedding subtitle tracks (SRT, ASS, PGS), and including chapter markers and attachments. For media server libraries (Plex, Kodi, Jellyfin), MKV provides better metadata handling and subtitle support than WebM.
The conversion can also re-encode VP9 to H.264/H.265 for broader device compatibility while staying in the Matroska container family.
For remuxing, FFmpeg copies VP8/VP9 video and Vorbis/Opus audio from WebM directly into MKV without re-encoding — since MKV is WebM's parent format, this is always lossless. For codec change, video is transcoded to H.264/H.265 and audio can remain or be converted. Additional tracks (subtitles, audio, attachments) are muxed in during conversion.
Remuxing is lossless — the bitstreams are identical. The MKV container adds no quality overhead. If re-encoding VP9 to H.264, typical CRF values produce comparable quality at similar file sizes.
| Device | WebM | MKV |
|---|---|---|
| Windows PC | Partial | Partial |
| macOS | Partial | Partial |
| iPhone/iPad | Partial | Partial |
| Android | Native | Partial |
| Linux | Partial | Partial |
| Web Browser | Native |
Resolution: 1920x1080
Bitrate: 8-12 Mbps
H.264 recommended for fast processing
Resolution: 1080x1080
Bitrate: 3.5 Mbps
Square or 9:16 for Reels
Resolution: 1080x1920
Bitrate: 4 Mbps
9:16 vertical, under 60s ideal
Resolution: 1280x720
Bitrate: 5 Mbps
Under 140s, 512MB max
Resolution: 960x540
Bitrate: 2 Mbps
16MB limit for standard, 64MB for document
Resolution: 1280x720
Bitrate: 4 Mbps
WebM to MKV lifts codec restrictions from Google's web-focused container, enabling richer multimedia features while staying in the Matroska family.
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Funcționează oriunde
| No |
8MB free, 50MB Nitro
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| Caracteristică | WebM | MKV |
|---|---|---|
| Nume complet | WebM Video | Matroska Video |
| Extensie | .webm | .mkv |
| Cel mai potrivit pentru | Web optimized | Multiple audio tracks |