Is the Macbook's power brick autovolt?

Question

Autovolt = can be plugged in to both 110V and 220V.

Answer 1

Should be. The one on my older PowerBook is, so I'd guess the newer MacBook is, too. Look closely at the side. There's usually a label that will tell you the acceptable AC input voltage.

Answer 2

Practically every laptop power supply can handle anything from 100 V to 240 V and probably things outside that range at both 50 Hz and 60 Hz (and pretty much every other frequency as well).

So it should just work fine without regard for whether you plug it into a 110 V outlet or 230 V outlet (and those are the only two voltages used, though they are often different to using different values).

There should be a sticker on it that indicates such things as acceptable input voltages as well as output voltage which will tell you for sure and the manual should mention what the adapter can handle as well.