The Great Spotted Woodpecker is a pied woodpecker: black with a large white shoulder patch and scarlet underneath the tail. It is much larger than the other British pied woodpecker,Lesser Spotted Woodpecker. The Great Spotted Woodpecker is about the size of a Starling, while the Lesser Spotted Woodpecker is more sparrow-sized
The head is black and white: black crown and nape, white forehead, cheeks and throat. The back, wings and tail are black, except for the large white shoulder patches and smaller white spots on the wings. The underparts are whitish-buff with red underneath the tail (undertail coverts). The bill is grey coloured, the legs are grey-green and the eye is red.
The sexes are similar except that the male has a red patch on the nape and the female does not.
Juveniles have a red crown, pink vent and "blotchy" white shoulder patches.
As with other woodpeckers, the stiff tail feathers are used as a prop when it is clinging to a tree, and its toes are specially arranged with two pointing forwards and two backwards.
Their flight is very undulating as they completely fold their wings against the body between each series of several flaps.