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Lectures recorded from the back row, voice notes captured at arm’s length and old MP3s mastered quietly all have the same problem. Drop the file in, raise the gain while you listen, and download a louder version that doesn’t crackle.
Processing locally on your device
Overview
The booster changes the level of the whole file by a fixed number of decibels, from −12 dB (quieter) to +30 dB (much louder). Decibels are logarithmic: +6 dB doubles the amplitude of the waveform, and most listeners judge a sound as roughly twice as loud at around +10 dB. The sidebar shows the gain both in dB and as a percentage, along with the file’s original peak level, so you can see how much headroom you have before you start.
Digital audio has a hard ceiling at 0 dBFS. Any sample pushed past it is flattened, which is called clipping and sounds like crackle or harsh distortion. With Prevent clipping turned on (the default), the boosted signal passes through a fast limiter set just below the ceiling, at −1 dB. It catches the loudest peaks so that the rest of the recording can come up further. If you turn the limiter off and the chosen gain would push the peaks over full scale, the tool warns you exactly how many decibels over you are.
Preview and export use the same Web Audio processing chain, so what you hear while adjusting the slider is what you download. The preview updates while it plays, and you can click anywhere on the waveform to jump to a quiet or loud passage. Rendering the boosted file happens offline in your browser and is much faster than real time, typically a second or two for a song.
You can save the result as MP3, M4A (AAC), WAV, FLAC, OGG or Opus, with a choice of bitrate for the lossy formats and a size estimate before you export. WAV is written instantly in JavaScript. The compressed formats use FFmpeg compiled to WebAssembly, which your browser downloads once (about 31 MB) and then keeps cached, so later exports start immediately and even work offline. Videos are accepted too: the booster takes their soundtrack and saves it as an audio file.
| Original peak | Safe boost without limiter | Typical boost with limiter |
|---|---|---|
| −3 dBFS | Up to +2 dB | +3 to +6 dB |
| −6 dBFS | Up to +5 dB | +6 to +9 dB |
| −12 dBFS | Up to +11 dB | +12 to +15 dB |
| −20 dBFS | Up to +19 dB | +20 to +24 dB |
Drop an audio file (MP3, WAV, M4A, OGG, FLAC) or a video onto the booster.
Press Preview and drag the Gain slider until the level sounds right.
Leave Prevent clipping on unless you want the raw, unlimited boost.
Pick an output format and bitrate.
Click Boost volume, check the result in the player and download it.
Use cases
Recordings made far from the speaker often peak around −20 dBFS. A boost of 12–15 dB with the limiter on brings speech up to a comfortable level on laptop speakers and earbuds.
Messages recorded at arm’s length or through a speakerphone are easy to miss in a noisy room. Boost them before forwarding, or before transcribing so the words are easier to make out.
Tracks from older albums are often several decibels quieter than modern releases. Raising them a few dB keeps a playlist at a more even volume without reaching for the volume knob between songs.
Drop in a screen recording or phone clip whose audio came out too low, boost it, and pair the louder audio with the video in an editor or with the Add Music tool.
Pro tips
Answers to common questions about the volume booster.
As much as the file’s headroom allows: if it peaks at −12 dBFS, about 11 dB is safe. With Prevent clipping on, you can go further, because the limiter holds the loudest peaks just below full scale. Very large boosts on music can still sound squashed, since many peaks are being held down at once.
It doubles the amplitude of the waveform. Perceived loudness grows more slowly: most people hear about +10 dB as roughly twice as loud.
Yes. Gain raises everything in the file by the same amount, including hiss and hum. Run the recording through the Noise Reducer first if the noise becomes distracting.
MP3 and the other compressed formats use FFmpeg in WebAssembly, which your browser downloads once (about 31 MB). It is cached afterwards. WAV export doesn’t need it and is instant.
Yes. The slider goes down to −12 dB, which reduces the level to about a quarter of the original amplitude.
No. ToolEnhancer processes files on your own device inside the browser. They are never sent to, stored on or seen by our servers.
Yes. The volume booster is free to use with no sign-up, no watermarks and no daily limits.