Convert WebM to MKV — Free Online Converter
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
About WebM to MKV Conversion
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.
Why Convert WebM to MKV?
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.
Common Use Cases
- Adding SRT/ASS subtitle tracks to WebM video for multilingual media libraries
- Re-encoding VP9 WebM to H.264 MKV for broader player compatibility