At a glance
| Input | Any audio the browser can open |
|---|---|
| Output | MP3 or WAV |
| Gain | 1x to 10x, default 1.5x |
| Where it runs | Entirely in your browser — no file is uploaded to a server |
| Price | Free, with no account and no sign-up |
| Offline | Works with no connection after the first visit |
Normalising rather than just amplifying
Multiplying every sample raises the noise floor along with the signal, and anything that goes past the maximum is clipped — flattened into distortion that cannot be undone.
Normalising finds the loudest peak and raises everything by exactly the amount that brings that peak to the ceiling. It is the largest increase available without any distortion at all, which is usually what people actually want.
When there is no headroom left
If the recording already peaks near maximum but sounds quiet, the problem is dynamic range rather than level — a few loud moments with everything else far below them. Raising the peak achieves nothing.
Compression is the tool for that: it reduces the gap between loud and quiet so the whole thing can be raised. It is also what makes a quiet interview audible in a car, and what makes over-compressed music tiring to listen to.
What cannot be fixed
Boosting raises hiss, hum and room noise as faithfully as the voice. A recording made too far from the microphone has a poor signal-to-noise ratio baked in, and no amount of gain improves the ratio — it just makes both louder.
Frequently asked questions
Why does it sound distorted after boosting?
It clipped — the signal was pushed past the maximum and flattened. Normalising raises to the ceiling and no further, which avoids it entirely.
It still sounds quiet even at maximum. Why?
The peaks are already loud and the rest is not. That is a dynamic range problem, and compression rather than gain is the answer.
Can it remove background hiss?
No — boosting raises the noise with the signal. The ratio between them was set when the recording was made.
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