Online Audio Mastering
Upload a finished mix and get a release-ready master in seconds: tonal balance correction, gentle multiband compression, stereo width, and a look-ahead true-peak limiter that hits your loudness target exactly. Compare the result with the original at matched volume, then download a 24-bit WAV or MP3. Everything is processed on your own device.
Last updated:
Tip: press A / B while playing (or the keys A and B) to switch instantly at the same position. Level-match plays both at the same loudness so you judge tone and punch, not volume.
Before and after
Tonal balance (octave bands)
How to use the Online Audio Mastering
- Open your mix (WAV or FLAC is best). A quiet demo mix is loaded so you can try it first.
- Pick a preset and a loudness target: -14 LUFS suits streaming services; choose -9 LUFS only for loud club or EDM releases.
- Fine-tune the tonal balance EQ, compression and stereo width if you like, and keep the -1 dBTP ceiling for streaming.
- Press Start mastering. Processing runs in your browser and usually takes a few seconds per minute of audio.
- Compare A and B while playing (tick Level-match A/B to judge tone, not volume), then download a WAV or MP3 master.
Loudness targets by platform
Streaming services measure the integrated loudness of every track (ITU-R BS.1770 / LUFS) and turn louder songs down during playback. Mastering louder than the normalization level does not make a song louder for listeners, it only reduces its dynamics. The values below are the platforms' published defaults as of 2024; they can change, and some apps let listeners switch normalization off.
| Platform | Playback normalization | Suggested master | True-peak ceiling |
|---|---|---|---|
| Spotify | -14 LUFS (default "Normal") | -14 LUFS | -1 dBTP (-2 if louder than -14) |
| YouTube | about -14 LUFS (turns loud tracks down only) | -14 LUFS | -1 dBTP |
| Apple Music (Sound Check) | about -16 LUFS | -16 to -14 LUFS | -1 dBTP |
| Amazon Music, Tidal, Deezer | about -14 to -15 LUFS | -14 LUFS | -1 dBTP |
| Podcasts (Apple guideline) | -16 LUFS stereo | -16 LUFS | -1 dBTP |
| Club / DJ use, CD | None | -11 to -8 LUFS | -0.3 to -1 dBTP |
The mastering chain, step by step
| Stage | What it does here | Control |
|---|---|---|
| 1. Tonal balance EQ | Measures 9 octave bands (63 Hz to 16 kHz) and moves each toward a smooth reference curve by up to ±4 dB, plus the preset's tilt | Tonal balance EQ %, preset |
| 2. Multiband compression | Splits into low (<120 Hz), mid and high (>2.5 kHz) bands with 4th-order Linkwitz-Riley crossovers; each band gets a soft-knee compressor with its own attack and release | Multiband compression % |
| 3. Stereo width | Mid/side processing of mids and highs; the low band can be kept mono | Stereo width %, mono bass |
| 4. Loudness gain + limiter | Raises the level until the integrated loudness meets the target, while a 2.5 ms look-ahead limiter holds 4× oversampled peaks under the ceiling | Target LUFS, ceiling |
| 5. Export | 24-bit WAV, 16-bit WAV with TPDF dither, or MP3 | Export format |
Reading the before and after report
- Integrated loudness (LUFS): the average perceived loudness of the whole track. It should land within about 0.2 LU of your target.
- True peak (dBTP): the highest inter-sample peak. It should be at or below your ceiling.
- Loudness range (LRA): how much the loudness varies between quiet and loud sections. Pop masters are often 4 to 8 LU; orchestral music can exceed 15 LU. A big drop means the master is much more compressed than the mix.
- PLR (peak-to-loudness ratio): true peak minus integrated loudness. Around 13 dB at -14 LUFS indicates healthy punch; below 8 dB sounds squashed.
- Limiter gain reduction: more than about 6 dB of limiting is often audible as pumping or dull transients. Lower the target or raise compression instead.
Tips for a better automatic master
- Export your mix as a 24-bit WAV that peaks around -6 to -3 dBFS, with no limiter or clipper on the master bus.
- Use Level-match A/B: louder almost always sounds "better" at first, so compare at equal loudness to judge tone and punch honestly.
- If vocals sound harsh after mastering, try the Warm preset or lower the tonal balance EQ amount.
- Master all tracks of an album with the same preset and target so they sit together; check the result with a LUFS meter.
Frequently asked questions
What does this online mastering tool do to my song?
It runs a typical mastering chain: a tonal balance EQ that nudges the octave-band spectrum toward a smooth reference curve, three-band compression to even out dynamics, stereo width adjustment with optional mono bass, and a look-ahead true-peak limiter. The gain into the limiter is adjusted until the integrated loudness matches your target within about 0.15 LU.
Which LUFS should I master to?
For streaming, -14 LUFS integrated with a -1 dBTP true-peak ceiling is a safe default: Spotify, YouTube and Tidal normalize playback to about -14 LUFS, and Apple Music to about -16 LUFS, so louder masters are simply turned down. Louder targets such as -9 LUFS are a stylistic choice for club and EDM tracks and reduce dynamics.
What is true peak and why -1 dBTP?
Sample peaks can miss the real peaks that occur between samples once audio is converted to analog or encoded to MP3/AAC. True peak estimates them by oversampling (4× here, as in ITU-R BS.1770). A -1 dBTP ceiling leaves headroom so lossy encoding by streaming services does not cause clipping.
How is loudness measured?
Integrated loudness follows ITU-R BS.1770-4: the audio is K-weighted, mean-square energy is computed in 400 ms blocks overlapping by 75%, blocks below -70 LUFS are ignored, then blocks more than 10 LU below the average are gated out. Loudness range (LRA) follows EBU Tech 3342 using 3-second short-term loudness.
What do the presets change?
Balanced applies only the automatic corrections. Warm adds about 1.5 dB below 250 Hz and softens the top end; Bright adds presence and air above 4 kHz; Punchy uses slower compressor attack so drum transients pass through, with a little extra low end; Gentle compresses less to keep more dynamics.
Is automatic mastering as good as a mastering engineer?
It gives a consistent, loud and balanced result that works well for demos, releases on a budget, podcasts and videos. A mastering engineer listens critically, fixes mix problems and makes artistic decisions an algorithm cannot. Start with a good mix that peaks around -6 dBFS with no limiter on the master bus.
Is my music uploaded?
No. Decoding, processing, measuring, A/B playback and WAV export all run in your browser with JavaScript and the Web Audio API. Only the MP3 encoder library is downloaded from a CDN if you export MP3.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.