Free MKV to MP4 converter

How do I convert MKV to MP4?

Add the MKV file above, keep MP4 as the output and click convert. If the video inside is H.264 or HEVC, which is common for screen recordings, it is moved into the MP4 without re-encoding, so the conversion is fast and keeps the full quality. Other codecs, such as VP9 and AV1, are re-encoded to H.264. Everything happens on your device; nothing is uploaded.

Why do recorders save MKV in the first place?

MKV (Matroska) is a robust container. If the recording app crashes, the computer loses power or the disk fills up, an MKV file stays readable up to the moment it stopped. An interrupted MP4 is often unreadable, because MP4 writes its index at the end. That is why OBS Studio has long recommended MKV for recording, and why many game and screen recorders use it.

The trade-off comes after recording. MKV is great for keeping a file safe and less great for sharing it: Safari, iPhones, many editors, slide decks and upload forms don’t accept it. Recording in MKV and converting to MP4 afterwards gives you both.

MKV vs MP4

OBS recordings: remux or convert?

OBS can remux MKV to MP4 itself under File › Remux Recordings, which is the quickest option if OBS is open. This page is the alternative when you’re on another computer, when someone sent you the recording, or when the video also needs a new codec or size: for example an AV1 recording that has to play on an older PC, or a 1440p capture you want at 1080p. Newer OBS versions can also record to a crash-safe hybrid MP4, which saves the conversion step altogether.

What about separate audio tracks?

MKV files can hold several audio tracks, such as your microphone and the system sound recorded separately. Many players only ever play the first audio track of an MP4, so viewers may hear only part of the sound. If your recording has separate tracks, set your recording app to also write a mixed track (OBS can record several tracks and mix one for you), or mix them in an editor before sharing. If you need captions, create a subtitle file with the subtitle generator.

What can’t be converted

The converter works with the codecs your browser can decode: H.264, HEVC on most current Macs and PCs, VP8, VP9 and AV1, plus common audio formats. Unusual codecs some MKV files carry, and professional formats such as ProRes, aren’t supported in a browser. The tool tells you when a file can’t be decoded.

Resolution and frame rate stay the same

The MP4 keeps the size and frame rate of the recording, so a 1440p screen capture at 60 frames per second stays 1440p at 60. That is what you want for editing. For sharing, a smaller file is often better: the video resizer scales it to 1080p or 720p, and fewer pixels mean a lighter file that still looks sharp in a chat window or a help article. Do the conversion first and resize afterwards, or resize straight from the MKV; either way, work from the original recording rather than a copy that was already re-encoded.

Tips

Keep the MKV until you’ve checked the MP4

Play the MP4 to the end and check the sound before deleting the original recording.

Trim and shrink in one go

Long recordings often need a trim before sharing. Use the video trimmer to cut the start and end, then the video compressor if the file is too large for email or chat.