Video Compressor

Convert MKV to MP4

Turn an MKV from OBS or anywhere else into an MP4 that editors, phones and websites take. H.264 and HEVC video is copied as it is.

Why MKV files need converting

MKV (Matroska) is a flexible container, and OBS recorded to it by default for years because an MKV survives a crash. But many video editors, phones, upload forms and social sites don’t accept MKV, even though the video inside is usually ordinary H.264 or HEVC. The same goes for many MKVs you download or get from other recording apps.

That video fits an MP4 as it is, so converting just moves it into the new container: no quality lost, and done in seconds even for hour-long recordings. The sound is kept as it is when it’s AAC or MP3; other audio, such as Opus or FLAC, becomes AAC, which every player reads.

Some MKVs hold video that MP4 players don’t read, such as VP9 or AV1; those are made H.264. MKVs can also carry several audio tracks and subtitles. The MP4 keeps the first audio track and leaves the subtitles out. If you need the other tracks, keep the MKV as well; the conversion never changes the original file.

Why convert MKV to MP4 here

  • Long recordings in moments

    Copying the video is as fast as reading the file, so even a two-hour OBS session is converted in about the time it takes to read it from disk.

  • Every frame kept

    The H.264 or HEVC video isn’t touched, so fast game footage keeps all of its detail, with no new blocks or blur from compressing it again.

  • Accepted everywhere

    Video editors, phones, Discord and upload forms all take MP4, the format that plays in every browser without a plugin or a separate player.

  • Done on your computer

    Your browser reads MKV, so a large recording is converted right there and not uploaded anywhere. That’s also why it’s quick: there’s no upload to wait for.

How to convert MKV to MP4

  1. 01

    Add the MKV

    Drop the recording on the page, or click to choose it from your Videos folder or wherever OBS saves it.

  2. 02

    Keep the video

    Leave Keep the video on to copy it as it is, or choose Make it H.264 for older players, TVs and editors.

  3. 03

    Download the MP4

    Play it on the page, then save it.

Questions

Can’t find your answer? Write to feedback@videocompressor.xyz.

Is converting MKV to MP4 lossless?

Yes, when the MKV holds H.264 or HEVC, as OBS recordings do: the video is copied into the MP4 untouched. VP9 and AV1, or Make it H.264, encode the video again at a high quality close to the original.

Why won’t my MKV play or import?

Many editors, phones and websites don’t read the MKV container, even when they can play the video inside it. Some open it but lose the sound, or can’t seek. As an MP4, the same video is accepted almost everywhere, from iMovie and phones to Discord and YouTube.

Can OBS record MP4 instead?

Yes. A plain MP4 is left unreadable by a crash or power cut, which is why OBS used MKV for so long, but OBS 30.2 added Hybrid MP4, which survives a crash, and OBS 32.0 made it the default for new setups. For MKVs you already have, OBS can convert them itself with File › Remux Recordings. This page does the same without OBS installed.

What happens to extra audio tracks?

The MP4 keeps the first audio track. If you recorded your microphone and game sound on separate tracks, the first one is the one OBS mixes everything into by default, so the MP4 still has all the sound you heard while recording.

Are subtitles kept?

No. Subtitles in an MKV are left out of the MP4, and they aren’t burned into the picture either. Keep the MKV if you need them, or use a player that loads subtitles from a separate file.

How big an MKV can I convert?

In your browser there’s no fixed limit, only your device’s memory and free storage. When an MKV has to go to our server, it can be up to 1 GB and 60 minutes long.

Can I convert MKV to MP4 on a phone?

Yes. Open this page in your phone’s browser and pick the MKV from your files. Phones that can’t open it send it to our server instead, and the MP4 is the same either way. The result downloads to your phone’s files, ready to share.

Is my recording uploaded?

Not when your browser can do it, which is nearly always for MKV. Otherwise it goes to our server over an encrypted connection and is deleted 2 hours after converting.

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