How to use it
- Open one file, or several for batch conversion.
- In Export choose the format, then the sample rate (keep, 44.1 kHz, 48 kHz…) and channels (keep, mono, stereo).
- Formats your browser cannot create are marked unavailable with the reason.
- Press Export for the timeline, or Batch → Convert all for every open file as a ZIP.
- Check the verification badge and download.
Which formats are available here
WAV is written directly by MusicCutter and is always available. MP3 uses the bundled lamejs encoder and works in every modern browser. M4A (AAC) and Opus use the browser's WebCodecs encoders and are only offered when a capability test passes in your browser; we never fall back to a server. FLAC export is not yet available.
Sample rate and channel conversion
Sample-rate conversion uses a windowed-sinc filter with anti-aliasing when lowering the rate. Converting to mono averages left and right. The export panel shows the estimated file size before you encode.
Questions
Does converting MP3 to WAV improve quality?
No. It stores the decoded audio without further loss, which is useful for editing, but it cannot restore what MP3 compression removed.
Can I convert a video to MP3?
If your browser can decode the video's audio track, yes: drop the video and export MP3.
Why is M4A not available in Firefox?
Firefox does not provide an AAC encoder to web pages. Use MP3 or Opus, or another browser.