spatch

The Hairy woodpecker is similar, but in my opinion, pretty easy to tell apart. The beak is quite noticeably longer, and overall the bird is just a lot bigger. A Downy is on par with perhaps a sparrow, while the Hairy is closer to the size of a Starling. There are other field marks, but they're quite fiddly, and I won't bore you with them.

Here is a good size comparison shot.