Convert MKV to MP4 — keep the quality, skip the upload

MKV files play without complaint on your computer, but iPhones, iPads, and many smart TVs stubbornly refuse to open them. OpenConvertVideo converts MKV to MP4 right inside your browser — often using your device's built-in encoder — with no account required and no file size limit.

Drop a file here, or click to choose

Converts right here — nothing uploads

Need trim, resize, or quality controls? Open the full converter →
  • No upload wait
  • Nothing leaves your device
  • Free, no account
  • No artificial size limits

Why convert MKV to MP4?

MKV (short for Matroska, named after the Russian nesting dolls) is a flexible container format capable of holding multiple audio tracks, subtitles, chapters, and almost any video codec under the sun. That flexibility comes at a cost: Apple has never built MKV support into iOS or iPadOS, so iPhones and iPads can't play it at all, and many smart TVs and video editors don't fare much better.

MP4 remains the universal standard for video delivery. Converting your MKV to MP4 ensures your video plays on any device without forcing anyone to install third-party media players or custom codecs.

Does the MKV contain H.264 or H.265?

If your MKV contains H.264 video, converting to MP4 H.264 is a straightforward container swap — quality loss is minimal even at the Balanced preset.

If your MKV contains H.265 (HEVC) — common with Blu-ray rips and high-quality downloads — you have two options: re-encode to H.264 for maximum device compatibility (some quality loss), or keep H.265 and output as an H.265 MP4. The H.265 MP4 plays natively on Apple devices and modern Android, and requires only the free HEVC extension on Windows 10/11.

Subtitles and multiple audio tracks

MKV files often contain multiple audio tracks (different languages, director's commentary) and embedded subtitle tracks. The converter outputs the first audio track. Subtitle tracks are not carried over — MP4 handles subtitles differently from MKV.

If you need to preserve subtitles, keep the original MKV and use a media player like VLC that can render MKV subtitles, or use a dedicated tool like Handbrake to burn subtitles into the video.

How it works

There is no upload step — processing starts the instant you select the file. For standard H.264 or H.265 video tracks inside the MKV, conversion can leverage your browser's built-in encoder, which is usually hardware-accelerated, so it often finishes quickly. A WebAssembly build of ffmpeg handles less common codecs as a fallback. All of that runs on your device, not ours — we only distribute the software, and your machine performs the conversion. Because zero data leaves your machine, there is no server queue and no file size limit either. Your MKV stays 100% private the entire time, as it should.

Frequently asked questions

Will subtitles be preserved?
No. Subtitle tracks aren't carried over during conversion. If you need them, keep the original MKV and play it in VLC, or burn the subtitles into the video using HandBrake before converting.
Can I keep the H.265 video instead of re-encoding to H.264?
Yes. Select H.265 as the output codec in the converter settings. The output will be an H.265 MP4, which plays natively on Apple devices and on Windows with the free HEVC Video Extension from the Microsoft Store.
Can I convert large MKV files?
Yes. Nothing is uploaded, so there's no server-imposed size limit. The practical limit is your device's available memory — most devices handle files up to several gigabytes without issues.
How long does conversion take?
Often just a few minutes. If your MKV holds standard H.264 or H.265 video, conversion can use your browser's built-in encoder, which is usually hardware-accelerated. Less common codecs fall back to the software engine and take longer, but either way there's no upload wait added on top.
My MKV contains Dolby TrueHD or DTS audio. Will it work?
These formats aren't decodable in browsers. The converter falls back to the AAC audio track if one is present, or may fail if TrueHD/DTS is the only audio track. In that case, HandBrake on desktop handles these formats.

Also on OpenConvertVideo