Convert MP4 to MKV

Transform your universal video format for web and devices into MKV format. Free, private, and browser-based.

How it works

  1. Upload MP4 Files — Drag and drop your MP4 files into the converter, or click to browse. Common sources: smartphones, screen recordings.
  2. Convert to MKV — The converter processes your files to MKV format entirely in your browser. No files are uploaded to any server — your privacy is guaranteed.
  3. Download Results — Download your converted MKV files instantly. For multiple files, download individually or as a ZIP archive.

Why convert MP4 to MKV

  • Convert to lossless MKV format to prevent further quality degradation during editing
  • Leverage MKV advantages: supports multiple audio/subtitle tracks
  • Overcome MP4 limitations: lossy compression — some quality loss
  • Upload to websites and platforms that require or prefer MKV format

FAQ

Is MP4 to MKV conversion free?
Yes, Fileza.io converts MP4 to MKV completely free with no limits on file size or number of conversions. No hidden fees, no watermarks, and no account required.

Will I lose quality converting MP4 to MKV?
Both MP4 and MKV use lossy compression. Output quality is excellent at high quality settings (85%+) — most people cannot see any difference.

Is it safe to convert MP4 to MKV online?
Absolutely. Unlike most online converters, Fileza.io processes your files entirely in your browser using WebAssembly. Your MP4 files are never uploaded to any server — the conversion runs on your own device, keeping your files 100% private.

Can I convert multiple MP4 files to MKV at once?
Yes, Fileza.io supports batch conversion. Drag and drop multiple MP4 files at once and they will all be converted to MKV simultaneously. Download them individually or as a ZIP archive.

Does MP4 to MKV conversion work on mobile?
Yes, the converter works on any device with a modern web browser — iPhones, iPads, Android phones, and tablets. No app installation required.

Will the converted MKV files be smaller or larger than MP4?
File sizes depend on content and quality settings. MP4 files are typically small to medium with h.264/h.265, while MKV files are varies by codec.

How long does MP4 to MKV conversion take?
Most conversions complete in seconds. The exact time depends on file size and your device performance. Since processing happens locally in your browser, faster devices convert more quickly. Video files may take longer due to re-encoding.