How to Master a Song Online for Free
You can master a song online for free in your browser with the Audio Master tool — no software to install, no account, and no upload, because the whole process runs on your own device with the Web Audio engine built into your browser. Pick a loudness target, nudge the EQ and dynamics, compare against the original, and export. The whole thing takes a few minutes.
Mastering here is real digital signal processing: a real EQ, multiband compression, stereo-width control, and a limiter, not an "AI mastering" black box. Every change happens in real time as you move a slider, so you can hear exactly what each control does instead of trusting a preset you can't see inside.
What "mastering" actually does (and what it doesn't)
Mastering is the final polish on a finished mix. It makes the track sit at a competitive, consistent loudness, evens out the tone, glues the elements together, and stops the loudest peaks from clipping. It is not a fix for a bad mix — if the vocal is buried or the bass is boomy in the mix itself, mastering only makes those problems louder. Get the mix as close as you can first, then master.
The one number that drives everything is loudness, measured in LUFS. Streaming platforms turn every track down (or up) to their own reference level on playback, so mastering to the right LUFS target is how you make sure your song lands where it should instead of sounding weaker than everything around it.
Master a song in the browser, step by step
1. Open the tool and drop in your track
Go to the Audio Master tool and drag your file onto the dropzone, or click to browse. It accepts MP3, WAV, FLAC, M4A, OGG, AAC, and WebM, up to five minutes long. For the cleanest result, master from the highest-quality mixdown you have — a WAV or FLAC rather than an already-compressed MP3.
The moment it loads, the tool decodes the file and measures its current loudness and peak level, showing both in the "Original" panel. That reading is your starting point.
2. Pick a genre preset as a starting point
Choose one of the genre presets — Flat, Warm, Bright, Punchy, or Vocal-Forward. Each one sets a sensible combination of EQ and compression so you're not starting from a blank slate. Flat leaves the tone untouched and just adds gentle glue; Warm lifts the lows and softens the top; Bright opens up the high end; Punchy leans into compression for impact; Vocal-Forward pushes the midrange where voices live.
Treat the preset as a rough draft, not a finished decision — you'll refine it in the next steps.
3. Choose a loudness target
Under Loudness target, pick where the song is going: Spotify (−14), YouTube (−14), Apple Music (−16), or Club / Loud (−9). The tool automatically works out how much level it needs to add to hit that target and drives the signal into the limiter to get there — the same way a real mastering chain does, rather than just turning everything up and clipping.
The "Mastered" panel updates with an estimated LUFS figure so you can watch it converge on the target as you work.
4. Shape the tone with EQ
The five-band equalizer covers 100 Hz (low shelf), 250 Hz, 1 kHz, 4 kHz, and 8 kHz (high shelf), each adjustable ±6 decibels. Small moves go a long way at the mastering stage — a boost or cut of 1 to 2 dB is usually plenty. If the low end feels thin, add a little at 100 Hz; if the track sounds dull, lift 8 kHz; if vocals feel boxy, try easing 250 Hz down slightly.
There's also a rumble filter (a high-pass filter, adjustable from 20 to 100 Hz) that clears out sub-bass energy you can't hear but that still eats into your headroom.
5. Set compression and stereo width
The Compression control has four settings — Off, Gentle, Firm, and Aggressive — driving a three-band (multiband) compressor. Compression reduces the dynamic range of the track, making quiet parts louder relative to the peaks so the whole song feels more even and controlled. Gentle or Firm suits most music; save Aggressive for genres that want an in-your-face, wall-of-sound feel.
Stereo width runs from Mono through Normal to Wide. Widening can make a mix feel bigger, but push it too far and the center — where your kick, bass, and lead vocal usually sit — can start to feel hollow. Nudge it, then check.
6. A/B against the original — fairly
Hit play and use the Hearing: Mastered / Hearing: Original toggle to switch between your master and the untouched file. This comparison is level-matched: both versions play back at the same loudness, so you're judging whether the master actually sounds better, not just louder. Louder almost always sounds "better" at first, which is exactly the bias level-matching removes. If the master doesn't clearly win the blind, honest comparison, keep tweaking.
7. Export your mastered track
Choose an export format — WAV (lossless, the safe default), MP3, or Opus — and click Export mastered. On export, the tool renders the full song through the chain, does a final full-length loudness measurement, and corrects the level once if the limiter pulled it slightly off target, so the number you asked for is the number you get. The file downloads as mastered_yourtrack.wav (or your chosen format). Because everything runs locally, your audio never leaves your device at any point.
Keep peaks under control
A master that clips sounds harsh and distorted, and once the audio is clipped that damage is baked in. The tool's limiter holds true peaks to roughly −1 dB automatically, which leaves a small safety margin of headroom below 0 dB — enough to survive the lossy encoding that streaming platforms apply without introducing new peaks. You don't have to set this manually; it's part of the chain. But it's worth understanding why your master tops out just below the ceiling instead of slamming right into it.
Mastering vs. just normalizing
If all you need is for a batch of files to play back at a consistent volume — spoken-word episodes, samples, a playlist of your own tracks — you may not need full mastering at all. In that case, reach for the volume normalizer, which matches loudness to a target without touching the tone or dynamics. Our guide on how to normalize audio volume walks through when normalizing is the right, lighter-weight choice.
Mastering is the bigger job: it changes tone, dynamics, and width, not just level. Reach for it when a song is finished and you want it to hold its own next to commercial releases.
A note on your mix before you master
The cleanest masters come from mixes that already have room to work with. If your mix is already crushed to the ceiling, the master can't do much except make the crushing more obvious. Leaving a few dB of headroom and paying attention to gain staging throughout the mix gives the mastering chain something to shape. When in doubt, turn the whole mix down a little before you export it, then let the master bring the level back up in a controlled way.
Frequently asked questions
Is it really free to master a song online here? Yes. The Audio Master tool is completely free with no account, no sign-up, and no watermark or export limit. There's no paid tier or trial gate — you can master as many songs as you want. It runs entirely in your browser using the built-in Web Audio engine, so there's no software to buy or install either.
Does my song get uploaded to a server? No. All processing happens locally in your browser on your own device, so your audio never leaves your computer. Nothing is sent to a server for mastering, which also means there's no upload wait — the track is ready to work with as soon as it decodes, and each slider change is applied in real time.
What LUFS should I master to? It depends on where the song will be heard. Spotify and YouTube normalize to around −14 LUFS, Apple Music to roughly −16 LUFS, and a loud club master might sit near −9. The tool has one-click presets for each. When in doubt, −14 LUFS is a safe, widely compatible target for streaming, and it's the level most platforms reference against.
Can mastering fix a bad mix? Not really. Mastering is a final polish — it evens out tone, controls dynamics, and sets loudness across the whole track, but it works on the mix as a single stereo file. It can't turn up a buried vocal or tame one boomy instrument in isolation. Fix balance problems in the mix first, then master the finished result for the best outcome.
What file format should I export? Export WAV if you want a lossless master to archive or send for distribution — it's the highest quality and the safe default. Choose MP3 for a smaller file that's easy to share or upload directly, or Opus (where your browser supports it) for efficient streaming-style compression. If you plan to do anything further with the track later, keep a WAV copy so you're not stacking lossy compression.