How serious is a small milk spill on a MacBook?

It may turn out completely fine, especially since you shut it down quickly and the spill was small, but there’s no reliable way to know without seeing where the milk went. Some liquid-damaged laptops work for weeks or months before corrosion causes trouble, so professional cleaning is worthwhile even if it starts normally. The power button itself isn’t automatically ruined, but milk underneath it could leave residue or affect the surrounding circuitry.

If you’re comfortable working on electronics, the residue can be cleaned with high-purity isopropyl alcohol after disconnecting the battery and carefully opening the laptop. It still needs plenty of time to dry afterward, and cleaning isn’t a guarantee if the spill already damaged a component. For most people, a repair shop is the safer option because MacBooks can be difficult to disassemble.

Milk is more concerning than plain water because it dries into a sticky, potentially conductive residue. Even if the Mac seems fine initially, residue can later cause corrosion or make keys stick. Keep it fully powered off and have a qualified repair technician open and clean it rather than relying only on surface drying.

Don’t keep testing the power button or turning it on to see whether it works. Liquid damage can cause a short, and powering it up may make a small problem worse. Leave it disconnected and upside down while arranging an inspection. A proper repair involves disassembly and cleaning the affected parts, not just wiping the keyboard.