Choose WEBM video files
Add non-empty .webm files up to 100 MB that host FFmpeg can open and that contain a video stream.
Free online WEBM to MKV converter
Create a new H.264 MKV from a WEBM video.
Fileverses processes eligible WEBM uploads one at a time on the server, creating an MKV with the first video stream and AAC audio only when the source supplies audio.
- H.264 video
- AAC when available
- 100 MB per file
Processed by our self-hosted conversion engine
Supported files
WEBM in. Fresh MKV out.
WEBMMKV
The fixed profile re-encodes the first WEBM video stream as H.264. If a first audio stream exists, it becomes AAC; it is not a container swap.
How it works
Convert WEBM files to MKV deliberately.
Start the server queue
Each upload is converted in sequence using H.264 video and conditional AAC audio settings.
Inspect each MKV
Download each separately named result and test it in the player or workflow that needs it.
Output boundaries
One selected program stream pair.
The result carries the first video stream and, if present, the first audio stream. Metadata, chapters, subtitles, attachments, and other tracks are removed.
Convert WEBM to MKVFirst video, optional first audio
The profile maps the first video stream and only the first audio stream when one exists. A video-only WEBM yields a video-only MKV.
New codecs, not a remux
Video is newly encoded as H.264 at CRF 23 and audio, when present, as AAC at 160k. Source codec bytes are not copied.
Source structure is removed
Metadata and chapters are removed; subtitles, attachments, alternate tracks, and other source streams are not retained.
No conversion controls
There are no trim, resize, codec, bitrate, quality, or stream-selection settings. A readable non-empty WEBM must be 100 MB or smaller.
WEBM to MKV help
MKV conversion facts.
What does Fileverses put in the MKV?+−
It writes H.264 video from the first video stream and AAC audio at 160k only when the WEBM has a first audio stream.
Can I convert a WEBM without audio?+−
Yes, provided it has a readable video stream. The resulting MKV has no audio track in that case.
Is WEBM converted to MKV without re-encoding?+−
No. This route re-encodes video and any mapped audio; it is not a container-only remux.
Does it preserve subtitles or all tracks?+−
No. Only the first video stream and optional first audio stream are mapped. Subtitles, attachments, alternate tracks, metadata, and chapters are removed.
What are the file limits?+−
Each upload must be a non-empty .webm file of 100 MB or less that host FFmpeg can read.
Can I resize or choose H.264 quality?+−
No. The profile has fixed settings: H.264 CRF 23 with a medium preset and AAC at 160k when audio exists.
Will every app play the MKV?+−
Compatibility depends on the receiving app and its MKV/H.264 support. Test the completed download in the intended destination.