Online Mastering: What It Is and How to Get It Right
Mastering used to mean booking time in a specialist studio with a dedicated engineer and a carefully treated acoustic environment. For most independent artists, that was often unaffordable or logistically impractical.
Online mastering has changed that. The question is no longer whether you can access mastering - it is how to use it well.
What mastering actually does
Mastering is the final stage of audio production before a track goes to distribution. It takes your finished stereo mix and prepares it for release - applying overall EQ, dynamics treatment and limiting to ensure the track translates well across different playback systems and meets the loudness standards of streaming platforms.
It is worth being clear about what mastering cannot do. It cannot fix a bad mix. If your vocal is buried, your bass is fighting your kick, or your low end is uncontrolled, mastering applies processing to the whole stereo file and has no way to address individual elements separately. A well-mastered track starts with a well-mixed one.
For a proper explanation of the difference between mixing and mastering and when you need each, AI Mixing vs AI Mastering: What's the Difference? covers it.
How online mastering works
Online mastering services follow the following process:
You upload your finished stereo mix as a WAV file. The service analyses the track and applies mastering processing - EQ to adjust tonal balance, compression and limiting to control dynamics and set the final loudness, and stereo enhancement if needed. You receive the finished master as a WAV file ready for distribution.
AI-based tools do this automatically and return a result in minutes. Engineer-based online services do it with human hands and ears, typically within a few days and with a revision round included.
The result of either route is a master file that is ready for distribution - provided the mix you submitted was in good shape to begin with.
Preparing your mix for mastering
How you prepare your mix before uploading has a direct effect on the quality of the master. These are the things that actually matter:
Leave headroom. Your stereo mix should peak no higher than -3dB to -6dB true peak. If your mix is already hitting 0dB consistently, the mastering stage has very little room to work. Bring the overall level down before you export.
Remove bus limiting. If you have a limiter or heavy compression on your master bus, remove it before you export for mastering. The mastering stage applies its own dynamics treatment - stacking your compression on top produces a squashed, flat result. Export clean.
Export as WAV at your full session sample rate. Do not export as MP3 or any other compressed format. Export at your session sample rate - typically 44.1kHz or 48kHz - at 24-bit depth. This gives the mastering process the full quality of your mix to work with.
Check your mix before you submit. Before uploading to any mastering service, run your mix through Mix Check Studio. The tonal balance, loudness and mono compatibility analysis takes under a minute and flags obvious problems before they go into the mastering stage. Free, no account needed.
Understanding LUFS targets
LUFS - Loudness Units relative to Full Scale - is the measurement streaming platforms use to normalise playback levels. Each platform plays audio back at a consistent loudness level, turning louder tracks down to match their target.
The targets to know:
Spotify normalises to -14 LUFS integrated on normal playback
Apple Music normalises to -16 LUFS integrated
YouTube normalises to -14 LUFS integrated
Tidal normalises to -14 LUFS integrated
If your master is significantly louder than these targets, the platform turns it down - and the benefit of aggressive limiting disappears. Mastering to approximately -14 LUFS suits most streaming releases, with the target adjusted slightly for your genre.
For a full breakdown by platform and genre, What LUFS Should I Master At? covers it in detail.
AI online mastering vs engineer online mastering
Both routes produce release-ready masters. The choice comes down to budget, timeline and what the project needs.
AI online mastering processes your track automatically, returns a result in minutes and costs significantly less than working with an engineer. Automix applies mastering as part of the full mixing workflow - if you have stems, the mix and master are handled together, producing a considerably more thorough result than any stereo-only mastering tool can deliver. If you only have a finished stereo mix, standalone AI mastering is also available.
Engineer online mastering brings human judgment, specialist genre expertise and a revision process. It costs more - typically £50-£200 per track for experienced independent engineers, more for established names - and takes days rather than minutes. For a significant release where the creative nuances matter and the budget is there, it is worth the investment.
The two approaches are not mutually exclusive. Many independent artists use AI mixing and mastering for regular releases and book an engineer for key singles or albums.
One check before you distribute
Before you submit your master to a distributor, run the final file through Mix Check Studio one more time. Check the loudness reading against your platform targets, verify mono compatibility - a master that sounds full in stereo can lose significant low end in mono, which affects phone speakers and most Bluetooth devices - and confirm there are no clipping issues.
It takes under a minute and catches problems before a listener does.
For everything that comes after the master - distribution, playlist pitching and what happens once your track goes live - How to Release a Song Independently covers the full picture.