Convert MKV Video to MP4, Free and Private

Convert MKV video to MP4 in your browser — useful since MKV isn't supported by most phones or Apple software.

Universal File Converter: Private & Fast

Convert images, videos, audio, and documents directly in your browser. Your files never leave your device, ensuring 100% privacy and security.

Video & Audio Converter

Extract audio from video or convert audio files between popular formats.

Drop your file here, or browse

Maximum file size: 50 MB

Supported: MP4, MOV, AVI, WEBM, MKV, MP3, WAV, FLAC, M4A, OGG

Output format

Advanced Media Tools

Extract Audio Trim Video

100% In-Browser Processing

Your files are processed strictly in local device memory. Nothing is uploaded — see how, and check for yourself.

How It Works

How to convert files with DuckConvert

Select Your File

Choose the file you want to convert from your device or drag and drop it into the converter.

Choose Output Format

Select your desired output format and any specific settings for your conversion.

Convert & Download

Click "Start Conversion" and wait for the local process to finish, then download your new file.

Don't take our word for it

This conversion runs entirely in your browser — nothing is uploaded. See exactly how, and check for yourself using your browser's DevTools Network tab.

How It Works

Conversion Mechanics

MKV is a popular container for downloaded or ripped video because it can hold multiple audio tracks and subtitle streams, but it isn't natively supported on iPhones, iPads, or by QuickTime, and plenty of Android phones and smart TVs choke on it too. Converting to MP4 gets you a file that plays back natively almost everywhere — note that only the primary video and audio track carry over, so separate subtitle or secondary audio tracks inside the MKV are not preserved.

Why It's Private

Runs Entirely In Your Browser: Files are decoded and re-encoded strictly in local memory.
No Network Requests: The converter makes no calls to any server — check your browser's DevTools Network tab to confirm.
Nothing to Sign Up For: No account, no upload, and no server-side storage of your files.
Runs On Your Hardware: Processing uses your own device's CPU via Web Workers, not a remote server.

Step-by-Step MKV to MP4 Local Guide

Select File

Drop your .mkv file into the box above.

Configure

Confirm MP4 is selected as the output format.

Convert

Click Convert — transcoding runs locally using an in-browser FFmpeg build.

Save Result

Download the resulting .mp4 file.

Frequently Asked Questions on Secure MKV to MP4 Conversion

No — this keeps the primary video and audio track only. If you need embedded subtitles preserved, they'll need to be handled with dedicated subtitle tooling separately.

MKV is a flexible container format, but Apple devices and many smart TVs and phones only ship with players for MP4's more common codec combinations.

It depends on the video's length and resolution — longer, higher-resolution files take proportionally more time to transcode.