Softshell crab is a crab harvested in the brief window after it has molted its hard exoskeleton, while the new shell underneath is still soft and pliable. Crabs molt periodically to grow, and the new shell hardens within hours to a couple of days, so softshells must be caught and cooked quickly.
In the U.S., softshells are almost always blue crab, harvested along the Atlantic and Gulf coasts in the warmer months when molting peaks. The whole crab, shell included, is typically cleaned, then floured and fried or sautéed; the shell turns crisp while the meat inside stays tender and sweet. Common preparations include softshell crab sandwiches (po'boys), tempura, and pan-seared crab with butter and lemon.
Because harvesting depends on catching crabs at the right molt stage, softshells were traditionally a short-season delicacy, though improved handling has extended their availability.