Convert MKV to MP4

Convert MKV to MP4 online. H.264 MKV files are remuxed in seconds with no quality loss, and other codecs are re-encoded. No upload, no watermark.

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Why convert MKV to MP4?

MP4 is the most widely supported video format. Converting from MKV fixes "unsupported file" errors on phones, social sites, presentation apps and video editors.

How the conversion works

Matroska MKV files often already contain H.264 video. The tool first tries a fast, lossless remux that copies the streams straight into an MP4 container. If the codecs don't fit in an MP4, it re-encodes to H.264 video and AAC audio instead.

What is an MKV file?

MKV, short for Matroska Video, is an open container that can hold almost any codec: H.264, HEVC, VP9 or AV1 video, AAC, AC-3, DTS, FLAC or Opus audio, several audio languages, subtitle tracks and chapters. OBS saves recordings as MKV by default, and many downloaded films use it. iPhones, iPads, QuickTime, many smart TVs, Premiere Pro and most social sites don't open it.

How to convert MKV to MP4 without losing quality

Drop the .mkv file above and press Convert all. When the video inside is H.264 and the audio is AAC or MP3, the streams are copied into an MP4 unchanged. That remux takes seconds even for a long film and keeps the picture bit-for-bit identical. OBS recordings made with the default x264 encoder and AAC audio usually take this fast path.

Tracks that change

The MP4 gets the main video track and the main audio track. Extra audio languages and subtitle tracks are not carried over in most cases, because MP4 players handle them poorly. Save the subtitles first with Extract Video Subtitles if you need them. HEVC, VP9 and AV1 video, and AC-3, DTS or FLAC audio, are re-encoded to H.264 and AAC, which takes much longer and is a new lossy encode.

Encoding happens on your device

Video encoding runs in this browser tab, on your own device. There is no upload and no queue. Your device does all the work, so a large or long clip can take a minute or more.

Before you start

Input: MKV. Output: MP4. The settings appear before anything runs, so you can check them first. Your original file is never changed.

Video work uses a lot of memory and CPU. Try a short clip first and check that the sound and playback work. On a phone, split large batches into smaller ones.

Keep the original until you have opened and checked the result. The work happens in this browser tab, so the size you can handle depends on your device's memory, your browser and the file itself.