Does CutFast upload my file?
No. Conversion runs locally in your browser — your file stays on your device.
MP4 to MP3 Converter — Extract Audio from Video Online
Extract high-quality MP3 audio from any MP4 video instantly in your browser. No upload to server, no software install, no file size limit. Perfect for saving music from videos, extracting podcast audio, or creating audio clips from lectures and tutorials.
Frequently asked questions
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).
Why can’t I select some codecs?
Codec availability depends on your browser’s WebCodecs encoder support and the target container.
Which browsers are supported?
CutFast requires WebCodecs for the fast path. Latest Chrome / Edge are recommended.
Will converting reduce quality?
Remux does not. Transcoding may — you can raise the quality preset to reduce loss.
What formats do you support?
Common inputs include MP4/WebM/MOV/MKV. Outputs include MP4/WebM/MOV/MKV plus MP3/AAC/WAV.