Will every MKV file convert?

It depends on the codecs inside. MKV can hold almost any codec; H.264, HEVC, VP9 and AV1 video work when your browser can decode them, while older or rare codecs may not be readable in a browser.

Are subtitles and extra audio tracks kept?

The main video and audio tracks are converted. Extra audio tracks and subtitle tracks in the MKV are not carried into the MP4.

Are my files uploaded anywhere?

No. Every live tool on JustYourConvert opens and converts your files inside your browser, on your own device. Nothing is sent to our servers, and the result is saved straight from your browser.

Is JustYourConvert free?

Yes. Every tool is free, with no sign-up, no watermark and no daily limit. Clearly labeled ads keep it that way.

Is there a file size limit?

Only your device's memory. Because the work happens in your browser, very large files can be slow on phones and older computers. Each tool says its practical limit under the drop area.

MKV to MP4 Converter

Play MKV videos on more devices by converting to MP4.

100% Free
No Sign Up
Nothing Uploaded

MKV to MP4

Turn MKV videos into MP4 for TVs, phones and editors

Drag & drop a video

or click to browse. You can also paste.

MKV, or any video, up to your device's memory.

Result-

Processed on your device. Nothing is uploaded.

Need more? Compress or trim on JustYourVideo

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How to convert MKV to MP4

Three steps, all in your browser.

1
Add your video
Drop or choose a video file.
2
Choose settings
Pick the format and quality.
3
Download
Save the converted video.

MKV to MP4 Converter: what to know

MKV (Matroska) is a flexible open container that can hold almost any video and audio codec, plus several audio tracks, subtitles and chapters. That flexibility makes it popular for recordings and archives, and also explains why some TVs, phones and editors refuse it: they support MP4 but not MKV, or not the codec inside.

Many MKV files contain H.264 video and AAC audio, which MP4 holds natively. Those streams are copied into the MP4 without re-encoding, so the conversion is quick and lossless. Other codecs are re-encoded to H.264 and AAC so the file plays widely, which takes longer and is slightly lossy.

Support depends on the codecs inside your MKV and on your browser. H.264, HEVC, VP9 and AV1 video can be read when your browser and device can decode them; older or uncommon codecs may not be supported by WebCodecs. The main video and audio tracks are converted; extra audio tracks and subtitles are not carried over. Nothing is uploaded.

Popular uses

Playing recordings on TVs, consoles and phones
Importing videos into editors that don't accept MKV
Uploading to sites that require MP4
Converting game and screen recordings

Tips for the best result

If a file won't open, its codec is likely unsupported in your browser; try another browser.
Save subtitles separately in a subtitle editor if you need them.
Very large MKV files need lots of memory, so a computer works better than a phone.

Read how JustYourConvert works and our privacy details. Keep your original files and check a converted file before you replace anything.