Where to start

If you're new to mastering, start with What Is Audio Mastering?, then read Mastering vs Mixing so you know what to hand off. When you're ready to master your own track, How to Master Music Online walks through the steps.

Loudness and measurement

Targets only make sense once you know what they measure. LUFS Explained covers the numbers, True Peak Limiting covers the ceiling, and Why Your Master Sounds Quieter on Streaming covers what streaming normalization does to your master. For how loudness and dynamic range vary by genre, see Dynamic Range by Genre.

Processing

EQ in Mastering, Dynamic Range in Mastering, and The Mastering Chain, Explained cover the processing decisions in order.

Choosing a service

Compare online mastering services and free mastering tools before you decide. For vinyl, see Mastering for Vinyl.