Krabs resemble large mechanical crabs with four long slender scythe-like legs used for climbing and crawling along very steep slopes. Krabs' weak spots are the Eye of X.A.N.A. on the back of their heads. Their first laser is a base triple laser that is difficult to aim. Their second weapon is the same laser fired beneath it, and their third weapon is a bright blue beam of electricity also fired beneath it. This beam is believed to cause instant devirtualization when it strikes a foe. However, no one has ever been hit by the beam. They also have the ability to fire standard lasers from the lower set of lenses in a rapid battery, each dealing only 10 hp of damage.
Krabs can also use their long scythe-like legs as their third weapon which can cause instant devirtualization. This has never happened on Lyoko either. However, when they were materialized in the real world in the episode A Bad Turn, the Krabs used their legs to pin their victims to the ground. In the same episode, Ulrich was almost killed when a Krab nearly decapitated him, but was saved by an uncanny Tower Deactivation. Krabs usually travel and co-operate in groups of two to three, but are able to defend themselves alone. Because they are frequently used by X.A.N.A., Krabs are often defeated fairly easily by the Lyoko Warriors.
Krabs were only shown in sectors 1-4. It was not until X.A.N.A. 2.0 , that they were finally shown in Sector 5, becoming one of only a few monsters shown in this area. This same distinction applies to the Megatanks.