MKV to MP4 Converter

Convert MKV videos to universally compatible MP4 format. Free, no quality loss, no signup.

Drag and drop your MKV video here

Max file size 500MB. Free, no registration required.

How to Use

Click the upload area or drag and drop your MKV video file

Select your preferred output quality — high, medium, or low

Click 'Convert' to transform your MKV to MP4 format

Download your converted MP4 video file instantly

Why choose our converter?

Quality, speed, and security for all your conversions.

High-quality conversion

Precise file conversion without any loss of quality.

100% browser-based

Files never leave your device. All processing happens locally.

Works on all devices

Computer, tablet, or smartphone — any browser works.

Fast processing

Convert files in seconds with our optimized engine.

No registration

Start converting immediately. No sign-up needed.

Batch conversion

Convert multiple files at once to save time.

About This Tool

This free MKV to MP4 converter transforms your MKV video files into universally compatible MP4 format. MKV (Matroska) is an open container format popular for storing high-quality video, but many devices and platforms don't support it natively. Converting to MP4 ensures your videos play everywhere.

Why Convert MKV to MP4?

MKV files often won't play on iPhones, iPads, many Android devices, smart TVs, gaming consoles, or social media platforms. MP4 with H.264 video and AAC audio is the most universally supported video format. Here's when you need to convert:

Mobile devices — iPhone and many Android phones don't play MKV files natively
Smart TVs — Most Samsung, LG, and Sony TVs have limited MKV codec support
Social media uploads — YouTube, Instagram, TikTok, and Facebook prefer MP4 format
Video editing — iMovie, Final Cut Pro, and Premiere Pro work best with MP4 input
Sharing via email or messaging — MP4 files are more likely to preview inline

MKV vs MP4: Key Differences

Both MKV and MP4 are container formats — they hold video, audio, and subtitle streams. The key difference is compatibility:

MKV — Supports more codecs and features (multiple audio tracks, chapters, attachments). Best for archiving and local playback with VLC or similar players.
MP4 — Universally supported across all devices, browsers, and platforms. Slightly fewer features but works everywhere.

If you need maximum compatibility, MP4 is the right choice. If you're archiving and only playing through VLC, MKV is fine.

Quality Settings Explained

High (CRF 18) — Near-lossless quality. Best for archiving or when quality is the top priority. Larger file size.
Medium (CRF 23) — Excellent balance of quality and file size. Recommended for most uses.
Low (CRF 28) — Smaller file size with acceptable quality. Good for sharing via messaging apps.

Privacy and Security

FastConvert processes your video entirely in your browser using FFmpeg compiled to WebAssembly. Your MKV file is never uploaded to any server. This means instant conversion with zero privacy risk — your files stay on your device throughout the process.

Frequently Asked Questions

How do I convert MKV to MP4 without losing quality?

Select the 'High' quality setting, which uses a CRF value of 18 for near-lossless encoding. The video is re-encoded with H.264 codec and AAC audio at 128kbps, preserving visual quality while producing a universally compatible MP4 file.

Why won't my MKV file play on my phone or TV?

MKV is a container that can hold various codecs (H.265, VP9, etc.) that many devices don't support. iPhones, most Android phones, smart TVs, and game consoles have limited MKV support. Converting to MP4 with H.264 codec ensures playback on virtually any device.

Is this MKV to MP4 converter really free?

Yes, completely free with no limitations. There are no watermarks, no conversion limits, no file size restrictions beyond the 500MB maximum, and no account required.

Can I convert MKV to MP4 on Mac without installing software?

Yes. FastConvert runs entirely in your browser — Safari, Chrome, or Firefox on macOS all work. No Handbrake, VLC, or other desktop software needed.

Can I convert MKV to MP4 on Windows?

Yes. Open FastConvert in any browser on Windows 10 or 11 (Chrome, Edge, Firefox). No software download required. The conversion runs locally in your browser.

What's the maximum file size I can convert?

You can convert MKV files up to 500MB directly in your browser. For files under 50MB, conversion happens entirely client-side. Larger files may use our secure cloud processing for faster results.

Will subtitles be preserved when converting MKV to MP4?

Soft subtitles (separate subtitle tracks) in MKV may not carry over to MP4, as MP4 has limited subtitle format support. Hard-burned subtitles that are part of the video stream will be preserved.

How long does MKV to MP4 conversion take?

Conversion speed depends on your device's processing power and the video file size. A 100MB video typically converts in 30–60 seconds on a modern computer. Mobile devices may take longer.

Can I upload the converted MP4 to YouTube or Instagram?

Yes. MP4 with H.264 is the recommended format for YouTube, Instagram, TikTok, Facebook, and virtually all social media platforms. The converted file is ready to upload immediately.

Are my videos secure during conversion?

Absolutely. All conversion happens locally in your browser using FFmpeg WebAssembly. Your video files are never uploaded to any server, ensuring complete privacy and security.