How to use the MKV Converter converter
- Add filesClick “Choose Files” or drag them in. Each file is detected automatically, and you can mix different formats in one batch.
- Pick the output formatUse the “to” menu next to each file to choose the target format (MKV is preselected).
- Convert and saveHit “Convert”. Everything is processed on your device, then you can download each result or a ZIP of all of them.
About MKV
MKV Matroska Video
MKV is an open, flexible container that can hold many audio tracks, subtitles and chapters. It is popular for movies and anime, but iPhones, some TVs and editing apps do not support it natively.
- Compression
- Varies (H.264/H.265/VP9)
- Features
- Unlimited audio & subtitle tracks
- Origin
- 2002, Matroska.org
- Best for
- Movies with multiple languages
Why use ConvertMathly?
Files are processed on your device and never uploaded. Close the tab and they are gone.
No account, no daily cap, no queue and no watermark — convert as much as you want.
The same engine used by professional video tools, running in your browser via WebAssembly.
Windows, Mac, Linux, Chromebook, iPhone and Android — any modern browser, nothing to install.
Frequently asked questions
What formats does the MKV Converter support?
It accepts MP4, MOV, AVI, MKV, WEBM, FLV, WMV, 3GP, M4V, MPEG, MPG, TS, MTS, M2TS and more, and can output MP4, WEBM, MOV, AVI, MKV, FLV, WMV, 3GP, GIF, MP3, WAV, AAC, OGG, M4A, FLAC.
Is it really free?
Yes. ConvertMathly is free with no sign-up, no watermarks and no limits. The site is supported by ads.
Are my files private?
Completely. Conversion happens inside your browser — files are never uploaded to any server.
Why does the first video or audio conversion take longer?
A one-time download of the FFmpeg engine (~30 MB) is needed. It is cached afterwards, so later conversions start instantly.
Does it work on iPhone and Android?
Yes, the converter works in Safari, Chrome, Firefox and Edge on phones, tablets and computers.