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What is mastering?

Mastering is the final step before you release a song. It's the polish that makes a mix sound finished and consistent everywhere it's played — earbuds, a laptop, a car, a club PA. A good master does three things: it balances the tone so nothing is too boomy or harsh, it controls the dynamics so the quiet and loud sections sit together, and it raises the loudness so your track holds its own next to commercial releases on Spotify, Apple Music and YouTube.

Mixing vs mastering

Mixing balances the individual tracks inside a song — vocals, drums, bass, synths. Mastering works on the finished stereo file as a whole: tone, dynamics, loudness and stereo width. You mix so the parts sit together; you master so the song translates everywhere and sounds as loud and clean as a professional record. Read more on mixing vs mastering →

Loudness and true peak (LUFS, dBTP)

In plain language: LUFS measures how loud something actually sounds to a person, rather than how big its waveform looks — which is why two tracks can peak identically and still feel worlds apart in volume. True peak (dBTP) is the highest level the signal reaches between the digital samples, once a speaker or codec rebuilds the waveform. It can be higher than any single sample in the file, which is how a track that looks safe in your DAW still crackles on playback.

Loudness is measured in LUFS (Loudness Units relative to Full Scale). Streaming platforms normalise everything to around −14 LUFS, so pushing a master far louder than that just costs you dynamics — the platform turns it back down anyway. The other number that matters is true peak (dBTP): leaving a −1 dBTP ceiling prevents the inter-sample clipping that MP3/AAC codecs and phone DACs can introduce. Loopin Mastering measures and targets both automatically. Learn what LUFS means →

Master your song free, in seconds

Loopin Mastering is free and instant. Add a stereo mixdown as an MP3 or WAV, pick a feel that fits your genre, and hear the mastered version against the original instantly — loudness-matched, so you judge the tone honestly rather than just "louder sounds better". When it's right, download a mastered WAV at about −14 LUFS with a −1 dBTP ceiling. No account, no waiting, and your track stays private. Follow the step-by-step guide →, or see how to master for Spotify, Apple Music and YouTube →.

Is Loopin AI mastering?

Not in the machine-learning sense — and for your files, that's the advantage. Most tools sold as AI mastering upload your track to a server, run it through a trained model and send a render back. Loopin runs a real mastering chain — corrective EQ, multiband compression, character EQ, saturation, stereo width and a true-peak limiter — entirely inside your browser, and sets every level from live measurements of your actual audio.

People look for this in a lot of ways — AI audio mastering, AI music mastering, AI song mastering — and nearly always mean the same thing: master my track automatically, without paying an engineer. That outcome is identical here: streaming-ready audio mastering in seconds. The difference is that your unreleased song never leaves your device.

What "automatic" actually means here

Loopin measures your track before it touches it. It runs an FFT across the file to find the worst low-mid resonance and places a corrective cut exactly there. It measures integrated loudness to ITU-R BS.1770 — the same standard Spotify and Apple Music use to normalise your release — then renders the chain a second time to land on your target precisely. That's measurement and correction, not a guess, and it's why a quiet bedroom mix and an already-loud one both come out in the same place.

AI mastering vs professional mastering vs Loopin

For a major commercial release, a human engineer still hears things no automatic chain can. For everything before that — demos, singles, beat tapes, the song you want up this week — an automatic master that gets loudness, tone and peaks right is the difference between a track that translates and one that doesn't.

Free unlimited mastering, with no sign-up

Loopin Mastering is free with nothing attached: unlimited tracks, unlimited re-masters, no credits, no subscription, no render queue and no account.

Free mastering usually comes with a catch — a watermark, a render cap, a sign-up wall, or a queue you wait in. There isn't one here, and that isn't a trial that expires. It's a consequence of how the tool is built — the mastering runs on your own processor, not on a server we rent. There's no per-track cost on our side to pass on to you, no queue because nothing is waiting for a worker to free up, and no sign-up because there's nothing to store. Master the same song twenty times with different feels until one of them sounds right; nothing is counted.

Loopin Mastering exists because we make Loopin, a songwriting app for iOS. The tool is genuinely free and stays that way — if it helps you finish a song, we'd like you to try the app.

Mastering beats, vocals and podcasts

The chain is the same whatever you feed it. What changes is the feel you pick and the loudness target that comes with it.

Beat mastering — hip hop, trap and electronic

Instrumentals live or die on low end and transient punch. Start with Punchy (−11 LUFS) for hip hop and trap: it tightens the lows and sharpens attack without letting the kick duck the entire mix, because the compression is multiband rather than one compressor across everything. For club-focused electronic and EDM, Club (−10 LUFS) pushes hardest and widens the stereo image while keeping bass mono, so the low end still lands on a mono PA. Wide (−14 LUFS) suits melodic electronic where the sides matter more than sheer volume. If you're posting or selling beats, Punchy and Club are the two to A/B.

Vocal mastering — demos and singer-songwriters

For a vocal-forward record — a singer-songwriter demo, an acoustic take, a voice-and-guitar sketch — Crisp (−14 LUFS) adds air and detail without hardening the top end, and Warm (−15 LUFS) rounds the low-mids if the recording came out thin or the room was bright. Both hold on to more dynamic range than the club feels, which matters when the performance is the song. One thing to get right: master the stereo mixdown, not a raw vocal track on its own — the chain is built for a finished mix.

Podcast mastering — speech and spoken word

You can master spoken word here, with one caveat worth stating plainly: the chain is built for music, so there's no speech-specific processing — no de-esser, no dialogue gate, no voice mode. What it does give you is consistent, standards-compliant loudness, which is the thing podcast platforms actually care about.

Use Cinematic, which targets −16 LUFS — the figure Apple Podcasts asks for, and close enough to Spotify's −14 that listeners won't be reaching for the volume between your episode and the next one. The −1 dBTP ceiling stops the clipping that appears after platform encoding. Edit and level your dialogue first: this is a finishing step, not a repair tool.

MP3 or WAV: what to upload, what you get back

Upload an MP3 or a WAV — or any other format your browser can decode, which in practice covers M4A, AAC, FLAC and OGG in most current browsers. Give it a stereo mixdown of the finished song, not stems and not a single track.

MP3 mastering and WAV mastering run through the identical chain — what differs is how much detail is in the file to begin with. WAV in beats MP3 in. Mastering brings out detail, and an MP3 has already discarded some of it. Mastering an MP3 will still sound better than it did, but nothing can recover what the encoder threw away — so if you still have the WAV your DAW bounced, use that one.

What comes back is a 16-bit WAV at your file's original sample rate, dithered on the way down — the correct way to reduce bit depth without adding quantisation noise. WAV is what you want for distribution anyway: send it to Spotify, Apple Music, DistroKid or SoundCloud and let each platform encode its own compressed version. MP3 export isn't available yet.

Why mastering in the browser works

Browser mastering used to mean a worse version of the real thing. It doesn't any more. The Web Audio API gives a page the same building blocks a DAW plugin uses — filters, compressors, waveshapers and sample-accurate offline rendering — and today's phones and laptops have processing headroom that dedicated mastering rigs didn't have a decade ago.

That makes three things possible at once, which server-based tools have to trade off against each other:

Nothing is uploaded. Your unreleased song stays on your device. No copy on a server, no retention policy to read, no account tying the file to your name.

It's instant. Instant mastering elsewhere tends to mean "fast once your upload finishes". Here there's no upload, no queue and no round trip at all — the only wait is your own processor rendering the file, which for a typical song is seconds.

It's free without a catch. No server doing the work means no per-track cost, which is why there's no credit system to run out of.

The trade-off is real and worth naming: you're bound by your device, so a long file on an old phone takes longer than the same file on a laptop. And this is a mastering chain, not a repair tool — it can't rescue a mix that's fundamentally unbalanced. For that, go back to the mix. Mixing vs mastering →