Convert MP4 to MKV Online Free
Runs 100% in your browser — your files never leave your device.
MKV is the collector's container: flexible, metadata-friendly, and loved by media servers like Plex and Jellyfin. Convert an MP4 into MKV without uploading for typical sizes — bigger files process on our servers — delete them right after processing, or let them auto-delete within an hour.
How it works
- 1
Add your file
Drop your file in or click to browse. Small files never leave your device.
- 2
Convert
Large files automatically finish on our servers instead — delete them right after processing, or let them auto-delete within an hour.
- 3
Download
Save the result instantly — original quality preserved as much as the format allows.
About this tool
Converting MP4 to MKV
MP4 is the universal video container — H.264 video and AAC audio in a package every device, browser, and platform plays. MKV is the collector's container: flexible, metadata-rich, and the home of media libraries served by Plex and Jellyfin. Converting re-wraps (and where needed re-encodes) the video into the target container: MKV carries multiple audio tracks and rich metadata that media servers organize well.. The conversion runs in your browser for typical files, with larger ones finishing on our servers and auto-deleting within an hour.
What to check after converting
Play the result end to end — container conversions occasionally shift timing or drop a compatibility feature the source container allowed. Check that audio plays in sync and the video renders at full quality, and keep the original file untouched as your master.
Frequently asked questions
Does converting between containers reduce quality?
Re-wrapping a video without re-encoding is lossless; where the target codec requires re-encoding, a small quality step applies. The tool handles both cases transparently.
Is my video uploaded anywhere?
Small videos convert entirely in your browser. Larger ones process on our servers and auto-delete within one hour — nothing is kept.
Why would I choose MKV over MP4?
MKV carries multiple audio tracks and rich metadata that media servers organize well.