Does CutFast upload my file?

No. Conversion runs locally in your browser — your file stays on your device.

What’s the difference between remux and transcode?

Remux copies streams into a new container (fast, no quality loss). Transcode re-encodes (slower, quality depends on settings).

Codec availability depends on your browser’s WebCodecs encoder support and the target container.

CutFast requires WebCodecs for the fast path. Latest Chrome / Edge are recommended.

Remux does not. Transcoding may — you can raise the quality preset to reduce loss.

Common inputs include MP4/WebM/MOV/MKV. Outputs include MP4/WebM/MOV/MKV plus MP3/AAC/WAV.

Convert MKV → AAC locally in your browser with CutFast (WebCodecs). Remux when possible, transcode when needed — no uploads, no installs.