MKV to MP4 Converter Online — Convert Matroska Locally
Convert MKV to H.264 MP4 in your browser without uploading the Matroska video.
Loading local video processor…
About this tool
The local engine can read many MKV files even when the browser player cannot preview them, then produces a compatible H.264 MP4 with an optional AAC audio track.
How to use
- Choose a supported video smaller than 200 MB.
- Select the output option, then start local processing.
- Preview and download the new video before closing the page.
Features
- MKV extension validation.
- Works without native MKV preview.
- MP4 download with optional audio.
Common use cases
- Open an MKV in MP4-focused software.
- Prepare Matroska video for a browser.
- Create a more widely shareable copy.
Common issues and tips
- Not every codec that can appear inside MKV is included in the browser engine.
- Multiple audio tracks and subtitles are not all preserved; the primary video and optional audio are used.
Privacy
The video is processed locally in your browser with FFmpeg WebAssembly and is not uploaded to Tools12345.
Frequently asked questions
Why is there no source preview?
Many browsers cannot play MKV directly, but conversion can still work.
Are subtitles retained?
No, the current MP4 output does not copy subtitle tracks.
Are multiple audio tracks retained?
No, output focuses on the available primary audio track.