Convert mp4 to mkv
Converted on your device. Files never leave this tab. Output tops out around 2 GB.
Nothing is uploaded
The converter runs inside this page. Cut your network after it loads and it still works.
No account, no daily limit
No sign-up, no daily limit, no watermark, no queue behind other people's files. Batch as many MP4 files as you like.
Real MKV output
Encoded by ffmpeg, the same library the command-line tools use — not a renamed extension.
About MP4
MPEG-4 Part 14
An ISO container standard (ISO/IEC 14496-14) based on Apple's QuickTime format. It usually holds H.264 or H.265 video with AAC audio. Use it when a video has to play on any phone, browser, TV or editing app.
About MKV
Matroska Video
An open container first released in 2002 that can hold almost any video and audio codec, plus several audio tracks, subtitle tracks and chapters in one file. Use it to keep multiple languages and subtitles together; convert to MP4 for devices that do not read MKV.