Normalize audio
Bring a batch of recordings to the same comfortable loudness, on your own device.
- Nothing is uploaded
- Works offline after first use
- Open source
- No watermark · limit is your device’s memory; phones hold less
Normalize MP3, WAV and other audio to the same loudness in your browser, like Spotify does. It is free, needs no account and adds no watermark, and your files are not uploaded: everything runs in your browser on your device. The size limit is your device’s memory, and phones hold less; give the page a short while after your first run to save itself for offline use, and then it works offline.
Done
Open the network tab. Your files never appear in it.
Add files and run the tool to see every request this tab makes.
Your files are processed on this device and never sent to a server. Reload the page to clear everything from memory.
Normalizing sets each file to a target loudness, so a quiet voice memo and a loud music clip play at the same level. This page measures the loudness of the talking or music, ignoring pauses, and brings each file to about −14 LUFS, the level Spotify and YouTube use.
A limiter eases down any peak that would clip, so boosting a quiet file does not distort. Each file is saved in its own format unless you pick another, and nothing is uploaded: interviews, lectures and rehearsal recordings stay on your machine.
A typical use is a batch that comes from different places: podcast episodes recorded in different rooms, voice notes from several people, or tracks for a playlist taken from different albums. Drop them all, leave Normalize chosen, and each file is measured on its own. Quiet files are lifted, by at most 30 dB so a nearly silent file does not turn into hiss, and loud files are turned down. The note on each result shows the change in dB, so you can see what happened.
Leave Save as on Same as the original to keep each file's own format, at about its original bitrate for MP3, M4A and OGG. Normalize works on videos too: the picture is copied and only the sound is changed. The target is about −14 LUFS, the level Spotify and YouTube play at. Podcast apps often recommend about −16 LUFS, so a normalized episode is slightly louder than that, which is rarely a problem.
How it works
- Drop one or more audio files or videos, or tap to pick them.
- Normalize is already chosen. Keep the original format or pick another.
- Run it. Each file downloads when it is ready; several come as a zip.
In your browser, not on a server
Your browser decodes the sound with its own audio decoders. Every sample is multiplied by the gain you chose (or the gain that brings the gated loudness to about −14 LUFS), then a look-ahead peak limiter turns down only the moments that would pass −1 dBFS, easing in over 5 ms and out over 150 ms. The file is written again in your tab: MP3 by LAME in WebAssembly, WAV and FLAC by code in this site, M4A and OGG by the browser’s own encoders. For a video, Mediabunny (MPL-2.0) copies the picture packets unchanged and adds the new sound.
Compared with upload-based tools: Online volume boosters upload the recording or video, cap the file size, and often just multiply the samples so loud parts clip and crackle. Here nothing leaves your device and the limiter keeps boosted sound clean.
Verify it yourself. Give the page a short while after your first run to save itself for offline use, then turn off Wi-Fi or switch to airplane mode and run the tool again. Or open your browser's developer tools (F12, or Cmd-Option-I on a Mac), pick the Network tab, and watch it while you convert. The panel above does the same count for you.
Questions
Is this peak or loudness normalization?
Loudness. Peak normalization only lifts the single loudest sample to the top, which barely helps a recording with one loud cough. Loudness normalization matches how loud files sound.
Is it true LUFS?
Close to it. The level is the average power of the loud parts in 400 ms blocks, the same gating idea LUFS uses, without the frequency weighting. Files come out within a decibel or two of each other.
Will normalizing fix one person being quieter than another in the same recording?
No. Normalizing sets one gain for the whole file, so the balance inside the recording stays the same: if one speaker is 6 dB quieter than the other, they still are. It makes a file as a whole match your other files. Evening out voices within one recording needs a compressor or leveller in an audio editor.
Why did a file get quieter?
Because it was louder than the target. Loud masters, many music videos and some screen recordings sit well above −14 LUFS, so they are turned down to match the rest. That is the point of normalizing a batch. If you only want files louder, choose By an amount instead and pick how many dB.
Is the file uploaded anywhere?
No. There is no server in this process. The page is a static file and the work is done by code running inside your browser tab. Give the page a short while after your first run to save itself for offline use; then you can turn off Wi-Fi and it still works.
More video and audio tools
Volume booster
Boost a quiet recording, turn down a loud one, or even out a batch. Done on this device, never uploaded.
Trim video
Cut a clip out of a longer video without uploading it. Most cuts take seconds and keep the original quality.
Mute video
Take the sound out of a video, in seconds and without re-encoding. The video never leaves this device.
Resize video
Change a video’s resolution, from 4K down to 240p or to a width and height you choose. Resized on this device, never uploaded.
Other conversions
Guides
- How to increase audio volumeSimply turning up a quiet recording clips the loud parts before the quiet parts get loud enough. Here is a better way, and a free tool that does it without uploading the file.