The European tree frog is a small frog that can grow to 4,5 cm in size at most. The smooth, shining, usually leaf-green back and the white-yellowish to grey belly are separated by a dark stripe on its flank reaching from the nostrils, over the eye and the eardrum, to the groin, contrasting the green, and forming a dark spot near the hips. The hind legs are much larger and stronger than the fore legs, which enables to jump rapidly.