Octopus vs squid: how to tell them apart
Both are cephalopods, both are molluscs, and they solve completely different problems. See the octopus guide and squid guide.
Count the limbs
Octopuses have eight arms, all the same. Squid have eight arms plus two much longer feeding tentacles that shoot out to seize prey and retract — ten limbs in total, of two distinct types.
Body shape says where they live
Squid are streamlined torpedoes with fins along the mantle, built for sustained open-water swimming. Octopuses are soft, rounded and finless, built for crawling, squeezing and hiding on the seabed.
The internal shell
Squid retain a stiff internal remnant of the ancestral shell — the pen or gladius — that stiffens the body against swimming forces. Octopuses have lost it entirely, which is why they can pour themselves through a gap the size of their beak.
Suckers
Octopus suckers are simple muscular cups. Many squid have suckers reinforced with hardened rings, sometimes toothed or modified into hooks — gear for gripping struggling fish in open water.
Lifestyle and social behaviour
Octopuses are largely solitary ambush hunters and den-dwellers. Many squid species shoal, hunt in open water and communicate with rapid body-pattern changes visible to neighbours.
Lifespan and reproduction
Both are short-lived, typically one to two years. Female octopuses brood a single egg clutch, stop feeding and die after hatching. Squid generally spawn and die shortly afterwards without extended brooding.
Quick field test
Two limbs noticeably longer than the rest, fins on the body and a rigid torpedo shape means squid. Eight equal arms, no fins and a soft bag-like body means octopus.
Read the full squid wildlife guide for IUCN status, population context and sources — or donate to WARN to help fund the partner teams protecting wildlife on the ground.
