🎬 Video Converter
Convert MP4 to MKV — Free & Private
Convert MP4 to MKV to store your video in a flexible container that supports multiple audio and subtitle tracks.
✓ Free forever✓ No upload✓ No signup✓ Instant
Ready to convert your MP4?
100% in your browser · Powered by FFmpeg.wasm · No account needed
How to Convert MP4 to MKV
1
Open the Converter
Click "Convert Now" to open with MP4 → MKV pre-selected.
2
Upload Your MP4
Drag & drop your MP4 file or click Browse to select it.
3
Convert Instantly
FFmpeg.wasm processes your video locally — nothing uploaded to any server.
4
Download MKV
Your converted MKV file downloads automatically when ready.
Why Convert MP4 to MKV?
- 🎬 From MP4 — convert the world's most universal video format to any target format
- 📦 Flexible container — MKV supports multiple audio tracks, subtitles, and chapters in one file
- 🎬 Lossless remux — video stream is copied without re-encoding, preserving full quality
- 🌍 Open standard — royalty-free format supported by VLC, Plex, Kodi, and most players
- 🔊 Multi-track audio — store multiple language tracks in a single file
- 🔒 100% private — files never leave your device
Features
100% Private
Files never leave your browser. Powered by FFmpeg.wasm.
Instant
In-browser processing — no server queue, no waiting.
Free
No account, no fee, no watermarks. Ever.
Quality Preserved
Converts at the highest quality settings by default.
Mobile-Friendly
Works on any device — phone, tablet, desktop.
No Install
Nothing to download. Works in any modern browser.
Frequently Asked Questions
Quality depends on the target format. For lossless remux to MKV, quality is identical. For FLV/WMV, some re-encoding occurs at high quality settings.
Conversion speed depends on file size and your device. FFmpeg.wasm processes video locally in your browser.
Yes — 100% free, no limits, no watermarks, no account needed. Convertlo runs entirely in your browser.
No. All conversion happens locally using FFmpeg.wasm. Your files never leave your device.
Yes — there is no strict file size limit, though very large files may take longer depending on your device's memory.