Turn your MP4 into MKV, right in your browser — no upload, no signup.
MP4 to MKV Converter turns your .mp4 file into .mkv entirely in your browser. Repackage an MP4 into Matroska to add multiple audio tracks or subtitle streams later, or to match what a media server like Plex or Jellyfin organizes its library around. MP4 and MKV both wrap the same H.264/AAC video and audio in this app, so most conversions are a fast repackage rather than a full re-encode — quality stays essentially identical and even a large clip converts in seconds, not minutes. Add your file, click convert, and download the result — nothing you upload ever leaves your device.
Drag and drop your .mp4 files, or click to browse. You can add up to 5 at once.
Click Convert — MP4 and MKV usually just need repackaging, so it's typically done in seconds, even for a large file.
Save each .mkv file individually, or download every converted file at once as a .zip.
Your videos are processed locally and never leave your device.
Works straight in your browser — no software, no account, no email.
MP4 and MKV usually just get repackaged, not re-encoded, so there's no quality loss and no long wait.
Convert as many videos as you like, with no limits or hidden fees.
Turn your MP4 into MOV, right in your browser — no upload, no signup.
Turn your MOV into MP4, right in your browser — no upload, no signup.
Turn your MP4 into AVI, right in your browser — no upload, no signup.
Turn your AVI into MP4, right in your browser — no upload, no signup.
Turn your MKV into MP4, right in your browser — no upload, no signup.
Change your video's format in seconds, right in your browser — no upload, no signup.