The silverfish is a nocturnal insect typically 13–25 mm (0.5–1.0 in) long. Its abdomen tapers at the end, giving it a fish-like appearance. The newly hatched are whitish, but develop a greyish hue and metallic shine as they get older. It has two long cerci and one terminal filament at the tip of the abdomen between the cerci. It also has two small compound eyes, despite other members of Zygentoma being completely eyeless, such as the family Nicoletiidae.
Like other species in Apterygota, the silverfish is completely wingless. It has long antennae, and moves in a wiggling motion that resembles the movement of a fish. This, coupled with its appearance and silvery scales, inspires its common name. Silverfish typically live for two to eight years.
The silverfish is an agile runner and can outrun most of its predators (including wandering spiders and centipedes). However, such running is possible only on horizontal surfaces, as it lacks any additional appendages, and therefore is not fast enough to climb walls at the same speed.