Turnint AITools

MP4 to MKV converter

Video tools

Convert MP4 videos to MKV right in your browser — no upload, no watermark. When the codecs match it's a lossless remux; otherwise it re-encodes locally. Your video never leaves your device.

What is this MP4 to MKV converter?

A free, browser-based tool that converts a MP4 video to MKV. Add a file, preview it inline, and download the result. All processing happens locally in your browser, so your video is never uploaded and there is no watermark.

How to use it

  1. Add a MP4 file on the left (drag & drop or click) — it shows an inline preview.
  2. Pick a quality preset (used only when the video has to be re-encoded).
  3. Press “Convert & download” to get your MKV file. The first run downloads the ~30MB converter once.

Lossless remux vs re-encoding

MP4 and MKV are containers — what matters is the video codec inside. When the codec already fits MKV, this tool just repackages it (a "remux"): instant and completely lossless. Only when the codec isn't compatible — most often anything involving WebM — does it re-encode the video locally, which takes longer and is where the quality preset applies.

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