WEBM to MKV Converter
Need to convert this file type? Drop it below — or drop any other file and we'll auto-switch. Outputs are auto-deleted after 2 hours; share links expire after 4.
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Convert WEBM to MKV online
Use this WEBM to MKV converter to turn WEBM files into MKV right in your browser — ideal for high-quality video, multiple audio and subtitle tracks and archiving.
When should you convert WEBM to MKV?
- To reduce file size and make uploading and sharing easier
- When you need it for high-quality video
- When you need it for multiple audio and subtitle tracks
- To open your files in apps that prefer MKV
What happens to your file
WEBM to MKV is a full re-encode, not a container swap: the video is decoded and re-compressed with libx264 (H.264) at CRF 23, preset medium, and the audio is re-encoded to AAC at 192 kbps. Matroska has no faststart concept and no pixel-format restriction, so the stream is written as-is once encoded.
Settings this conversion runs with
| Engine | ffmpeg |
|---|---|
| Video codec | libx264 (H.264) |
| Video quality | CRF 23, preset medium |
| Audio codec | AAC |
| Audio bitrate | 192 kbps |
What changes
- The WEBM picture is decoded and re-compressed with libx264 (H.264), so this is a generation loss: the output is built from an already-compressed source, not from the original camera data. Converting WEBM to MKV and back will soften the clip a little more each time.
- Only one video and one audio stream reach the MKV file. Additional audio languages, embedded subtitle tracks, and chapter markers are not carried across.
About WEBM and MKV files
WebM video
Strengths
- small for the web
- open and royalty-free
Limitations
- limited support in some apps
- less common offline
MKV video
Strengths
- holds many tracks
- flexible container
- high quality
Limitations
- not supported on all devices
WEBM vs MKV
| Format | WEBM | MKV |
|---|---|---|
| Compression | Lossy | Lossy |
| Transparency | — | — |
| Best for | web video, open-source playback | high-quality video, multiple audio and subtitle tracks |
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Frequently asked questions
- Does converting WEBM to MKV re-encode the file?
- WEBM to MKV is a full re-encode, not a container swap: the video is decoded and re-compressed with libx264 (H.264) at CRF 23, preset medium, and the audio is re-encoded to AAC at 192 kbps. Matroska has no faststart concept and no pixel-format restriction, so the stream is written as-is once encoded.
- What should you know before converting WEBM to MKV?
- The WEBM picture is decoded and re-compressed with libx264 (H.264), so this is a generation loss: the output is built from an already-compressed source, not from the original camera data. Converting WEBM to MKV and back will soften the clip a little more each time.
- Is this WEBM to MKV converter free?
- Yes. You can convert WEBM to MKV online for free, with no account and no watermark.
- Do I need to install software or sign up?
- No. Use the converter from your browser without installing software or creating an account. Files are uploaded to our servers for processing.
- Will converting WEBM to MKV reduce quality?
- MKV uses lossy compression, so the file can get smaller while some visual quality may change.
- Are my files safe?
- Yes. Files are processed only to complete the conversion and are auto-deleted after 2 hours. We never share them.