twineconvert
Free · in-browser · no upload

MKV to MP4
Converter

Drop your MKV file. We'll convert it to MP4 right here in your browser, your file never leaves your device.

Local

Drop your file here

or click to pick from your device

.mkv
Nothing uploaded No file size cap Open source

How it works

Three steps. No upload, no signup.

  1. 1

    Drop your file

    Click the dropzone above or drag a MKV from your desktop. Files of any size, there's no upload, so there's no upload limit.

  2. 2

    Convert in your browser

    The conversion runs entirely in this tab using JavaScript and WebAssembly. Your file never touches our servers, we don't have any.

  3. 3

    Download

    Get your MP4 the moment the conversion finishes. Convert another, or close the tab.

Files stay on your device

Your file is never uploaded. The entire conversion runs in your browser using WebAssembly. We can't see what you convert because we have no server to see it.

No file size limit

Server converters cap free users at 1-2 GB and gate larger files behind a paid plan. Since nothing uploads, our limit is whatever your browser can handle.

Free, no signup, no ads on conversions

No account required. No watermark on the output. No queue. Open source, every line of conversion code is public.

Formats involved

About MKV and MP4

MKV, Matroska Video

MKV is an open-source container that holds essentially any video/audio codec combination plus subtitles, chapters, and metadata. The format of choice for high-quality video archives, fan-subtitled content, and anything that benefits from multiple audio tracks. The catch: not every player supports it, and converting MKV to MP4 is the standard fix for the won't-play-on-my-TV problem.

How to open

VLC reads everything MKV. Plex and Kodi handle MKV libraries. Browsers and many TVs do not, converting to MP4 makes MKV content universally playable.

Full MKV format guide →
MP4, MPEG-4 Part 14

MP4 is the dominant video container on the web, H.264 video plus AAC audio, in a structure designed for streaming. Every browser, mobile device, smart TV, and editing tool reads MP4. The format is technically a container (not a codec), so two MP4 files can have very different internal codecs, but the H.264+AAC default is what enables universal playback.

How to open

Every video player on the planet, VLC, QuickTime, Windows Media Player, browsers (HTML5 video), iOS, Android, smart TVs, game consoles. Universal.

Full MP4 format guide →

Related tools

Convert other files to MP4

How we compare

MKV → MP4 vs the alternatives

FeatureUstwineconvertCloudConvertiLovePDFFreeConvertSmallpdf
Files uploaded to a server
Free file size limitNo limit1 GB200 MB1 GB5 GB
Free conversions per dayUnlimited10/dayLimitedLimited2/day
Signup required
Watermark on output
Open source
Works offline (after first load)

Last verified May 2026 from each competitor's pricing and FAQ pages. Limits and pricing change frequently.

FAQ

Common questions

Is this MKV → MP4 converter really free?

Yes. No signup, no watermark, no daily file count limit. The entire engine is open source, you can read the conversion code on GitHub.

Where does my file go when I convert it?

Nowhere. The conversion runs entirely in your browser using JavaScript and WebAssembly. Your file is never uploaded to our servers. We don't have any servers handling files, there's nothing for us to log, store, or accidentally leak.

What's the maximum file size?

Whatever your browser can hold in memory. Practically, this means a few hundred MB on most computers, significantly larger than the 1-2 GB caps that server-upload converters charge for. Very large files (multi-GB) may require closing other browser tabs first.

Why convert MKV to MP4?

High-quality video archives with multiple audio/subtitle tracks. Web video, mobile video recording, video sharing. The most common reason to convert is compatibility, MP4 works in places where MKV doesn't, or vice versa.

How do I open a MKV file in the first place?

VLC reads everything MKV. Plex and Kodi handle MKV libraries. Browsers and many TVs do not, converting to MP4 makes MKV content universally playable.

Does this work offline?

Once the page is loaded, the conversion itself runs entirely offline. The first time you use a tool, your browser downloads the conversion library (a one-time cache). If you reload while offline, the page won't load, but you can install the site as a Progressive Web App for full offline use.

Can I convert multiple files at once?

Single file at a time for now. Batch conversion is on the roadmap, for now, drop one file, download the result, then convert the next.