Audio Normalizer Online - Match Loudness to -14 LUFS
Drop one file or a whole batch, pick a platform, press Normalize.
This audio normalizer online shows you the real loudness of every file before anything changes, then moves it to -14 LUFS or another target. It also shows the measured loudness of each finished file, and it never squashes a song harder to hit a number. Free, no upload, no signup.
How to Normalize Audio Online in 3 Steps
- Add your files. Drag them into the "Select Audio" box, or press it to browse. Under "Your files", each row shows "Before" loudness and an "After" note such as "needs +10.6 dB".
- Pick a target. Under "Target", press "Spotify -14", "Apple Music -16", "YouTube -14", "Podcast -16", "Broadcast -23" or "Custom". "Advanced: custom level, peak ceiling, file type" sets your own.
- Normalize. Press "Normalize", watch "normalizing 45%" and "checking the result...", then press "Download".
The first press starts the audio engine inside your browser, so the first wait is longer, then it is quick. The page shows "Starting the audio engine..." and "Measuring..." meanwhile.
What LUFS and True Peak Mean
LUFS is a number for how loud a whole file sounds to a person, averaged over its full length. Streaming platforms play tracks at a fixed LUFS number, so two songs at -14 LUFS play at the same loudness. Most of the time that means turning a loud song down.
True peak, written dBTP, is the highest point of the sound, including tiny peaks between samples that a normal peak meter misses. 0 dBTP is the absolute top. Anything that tries to go over it gets cut off flat, which is called clipping and sounds like a crackle.
Which Loudness Should You Pick?
| Target | Level | Who uses it |
|---|---|---|
| Spotify | -14 LUFS, -1 dBTP | Spotify's published guidance |
| Apple Music | -16 LUFS, -1 dBTP | Where Sound Check is widely measured. Apple does not publish it but asks for -1 dBTP peaks |
| YouTube | -14 LUFS, -1 dBTP | The level it plays at. It turns loud videos down but not quiet ones up |
| Podcast | -16 LUFS, -1 dBTP | Apple Podcasts. Spotify podcasts use -14 |
| Broadcast | -23 LUFS, -1 dBTP | EBU R128, the European TV and radio standard |
| Custom | -30 to -6 LUFS, ceiling -6 to 0 dBTP | Your own, under "Advanced" |
Spotify turns loud tracks down, which adds no distortion. It turns quiet tracks up too, but it leaves 1 dB of headroom for its lossy files.
Spotify's own example is a -20 LUFS track with -5 dBTP peaks, which only reaches -16 LUFS. So a quiet master stays quiet on Spotify unless you normalize it first.
For masters louder than -14 LUFS, Spotify asks for peaks under -2 dBTP, so use "Custom" with a -2 ceiling.
Why a Volume Booster Is Not the Same as Normalizing
A plain volume boost pushes the loudest point of a file to a level. A quiet song with one loud drum hit stays quiet, and a loud song with soft peaks can end up too loud.
Loudness normalizing measures how loud the whole file sounds and moves that number to the target. When you only want more volume and do not care about a target, you can turn one file up by a set amount instead.
What Happens When the Peaks Would Clip
The tool changes the level by one plain amount, the target minus the measured loudness, so loud and quiet parts keep their difference. If the peaks would then pass the ceiling, the table warns "peaks will be held" before you press anything.
Then a true peak limiter holds only those peaks at the ceiling. A limiter stops sound going above a set level, and this one checks at 4 times the sample rate to catch peaks between samples.
Holding peaks takes some loudness away, so the file can land under the target. The tool does not squash the song harder to force the number. The line under the button then reads "could not reach -14 LUFS without clipping, so its peaks were held and it sits a little lower".
Our test file (-19.5 LUFS, peaks at -0.1 dBTP) needed +5.5 dB for Spotify. With peaks held it came out at -17.6 LUFS and -1.7 dBTP as MP3, and -17.2 LUFS at -1.0 dBTP as WAV. For MP3 the tool aims 0.5 dB below your ceiling, because MP3 encoding pushes peaks up a little.
Batch Normalize MP3 Files to the Same Loudness
Drop many files at once, and use "Add more files" later. The button reads like "Normalize 3 files". Files run one at a time, so a batch never needs more memory than one file.
Each result is named like song-14lufs.mp3, and "Download all as zip" appears with 2 or more finished files. The tool sets no limit on file count or size, but very long files depend on your device's memory.
This is handy for an album, a podcast season or a lecture series. For talks, you may want to cut the long pauses out of a recording first. The page remembers your target, custom level, ceiling and file type on that device.
Hear the Difference Before You Download
Each finished file has its own "Play", a position bar and an "Original | Normalized" switch that flips while the file plays and keeps your position. Only one file plays at a time.
The card says how many dB louder or quieter the normalized version is. If the file was already close to the target, it says so, and the two sides sound almost the same. For a format the browser cannot play, such as AVI, the card says the download still works.
MP3 or WAV Download, and What the Tool Reads
Pick "MP3" or "WAV" as the "File type" under "Advanced". MP3 matches the closest standard rate of 128, 192, 256 or 320 kbps, which is how much sound data is used per second. In our test a 192 kbps file came out at 192 kbps.
WAV is uncompressed 16-bit at your file's sample rate, so it is much bigger. A 3 minute file was 4.1 MB as MP3 and about 30 MB as WAV, and you can shrink a big WAV afterward.
On our test computer, three files of 8 seconds, 10 seconds and 3 minutes were measured in 6 seconds. Making them took 14 seconds as MP3 and 6.5 seconds as WAV.
The tool reads MP3, WAV, M4A, AAC, OGG, FLAC, OPUS, AIFF and CAF, plus MP4, MKV, WEBM, MOV, AVI, M4V and 3GP video. Only the sound of a video is used, and the download is always an audio file.
Our 3 minute file measured -24.6 LUFS and came out at -14.0 LUFS by the tool's check and -13.9 LUFS on a separate meter. A -40.5 LUFS file came out at -14.1 LUFS, a change of +26.9 dB.
After every file is made, the tool measures the finished file again. LU means loudness units, the same scale as LUFS. If the result is off by more than 0.25 LU, the tool corrects the level once and remakes the file.
A file within 0.5 dB of the target shows "already at the target" and gets only that tiny change. A file under -60 LUFS shows "Too quiet to measure, it is nearly silent."
Measured and Normalized on Your Own Device
Nothing leaves your device. FFmpeg runs inside your browser to read, measure, normalize and re-measure the file, and the download is made there too. No account, no signup, no file limit we enforce, and settings stay in your browser.
Audio Normalizer FAQ
What LUFS should I normalize to for Spotify?
Press "Spotify -14", which sets -14 LUFS with a -1 dBTP ceiling, the numbers on Spotify's own loudness page. If your master is louder than -14 LUFS, Spotify asks for peaks under -2 dBTP, so use "Custom" with a -2 ceiling.
Why is my file a little under the target?
Its peaks would have clipped at the target level, so the tool held them at the ceiling instead. Holding peaks takes some loudness away, and the tool does not squash the rest of the file to make up for it. The table shows the real measured number.
Does normalizing change the sound quality?
It makes one plain level change, so the loud and quiet parts keep their difference. Only a file whose peaks have to be held gets its peaks limited. MP3 is encoded again at the matched bitrate, and WAV is lossless.
Can I normalize the sound of a video?
Yes, you can add a video such as MP4, MKV, WEBM, MOV or AVI. The tool measures and normalizes only the sound, so you get an audio file back and not a video.
Does it work on a phone?
Yes, it runs in your phone browser, and files are handled one at a time to keep memory low. Very long files still depend on how much memory your phone has.