Hitbox

From UltimateMK.com

A Hitbox is an invisible box attached to a character's animation that represents where they can be hit or what part of them is an attack area that can hit an opponent.

In 2D Mortal kombat, characters have at most 2 hitboxes. One of them represents where they can be hit. It is a box the full high of the character, about 25% of the character's width, and is located in the middle of their sprite. This means that when the characters leg is extended with a kick, their main hitbox may be actually in front of their body.

The other hitbox the characters can have is the attack box. They have this if they are current attacking. The attack box is usually a box that covers the entire part of them as it attacks.

Attack boxes are usually referred to as Hot Boxes. And boxes that represent where you can get hit are usually referred to as Cold Boxes.

In the 2D Mortal Kombat, the hitboxes for sweeps are a little strange. When you sweep someone, you do not have to hit their Cold Box, you just have to hit any part of the box that completely surrounds their animation. This means if they are doing a punch, sweeping under their fist will hit them.