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About Mono → Stereo
Mono → Stereo — free, private, browser-based audio tool
Convert mono recordings to a balanced two-channel stereo file. It takes audio and gives you MP3. It runs in your browser, so the file is processed on your own device.
Why use Mono → Stereo
- ·Files stay on your device — nothing is uploaded
- ·No signup needed
- ·Works in any modern browser, on any OS
- ·Free daily use; Pro removes limits and watermarks
How to use it
- 1Drop an audio file on the page, or click to choose one.
- 2Pick the options you want.
- 3Download the MP3 file.
What Mono → Stereo does
Convert mono recordings to a balanced two-channel stereo file. The result is a MP3 file you download directly.
How it works
Web Audio API + AudioWorklet for low-latency DSP, ffmpeg.wasm for codec encoding, and a custom WASM SIMD path for time-stretching and pitch-shifting. The processing code runs inside the page, so your file is not uploaded to a server — you can confirm this in your browser's DevTools → Network tab.
Frequently asked questions
Does Mono → Stereo upload my files?+
No. Mono → Stereo runs in your browser and processes the file on your device. Nothing is sent to our servers.
Is Mono → Stereo free?+
Yes, with a daily free allowance and no signup. Xonvert Pro ($4.99/month) removes the daily limits and the watermark on exported files.
Do I need to install anything?+
No. It works in any modern browser on Windows, macOS, Linux, ChromeOS, Android and iPad.
Related audio tools
Trim Audio
Cut the start and end of an audio file with precise time controls.
Merge Audio
Join multiple audio files back-to-back into one track.
Adjust Volume
Make audio louder or quieter — by dB or by percent.
Fade In
Smoothly ramp the start of your audio from silent to full volume.
Fade Out
Smoothly ramp the end of your audio down to silence.
Normalize Audio
Bring quiet tracks up to a consistent loudness — no clipping.