offlinewebtools.com browser-local workbench

MP4 to MKV Converter

Convert MP4 videos to MKV format, supporting multiple audio tracks, subtitles, and chapters in a flexible container.

Shipped

Browser local

Source file *

Files are processed locally in your browser using WebAssembly. This input is required.

Saved FFmpeg presets (stored locally)

Saved presets

Preset name

Preview and export

Inspect the source before running FFmpeg, then preview the generated output before downloading.

Local media

Choose a media file to fill this source preview before processing.

Expected output

The generated file preview, size, type, and download action appear here after processing.

Quality (CRF)

Lower = better quality (0-51, default: 23)

What this tool does

MP4 to MKV Converter helps you convert MP4 videos to MKV format, supporting multiple audio tracks, subtitles, and chapters in a flexible container.

What you get

MP4 to MKV Converter produces a direct output in this page and keeps all processing on your device, with nothing uploaded to our servers.

If this tool misbehaves, share a quick summary so we can investigate. We include the tool URL automatically—no need to copy and paste.