Headroom

Headroom is the safety margin between your signal's peak level and 0 dBFS, the point where digital audio clips. Leaving headroom means your loudest transients still have room to breathe without hitting the ceiling and distorting. During mixing, engineers typically keep the mix bus peaking well below 0 dBFS so the mastering stage has space to add processing, glue, and loudness without introducing artifacts. Headroom also matters inside individual plugins, since many analog-modeled processors are calibrated to sound best when fed a signal that leaves margin above it. Working with adequate headroom keeps your metering meaningful, your dynamics intact, and your options open at every later stage of production.