A hitbox is the invisible shape attached to a character or attack that the game uses to decide whether contact happened. When an attack hitbox overlaps a character hurtbox, the game registers a hit.
Players imagine fights as the art on screen, but the game judges a simpler world of boxes and capsules. Each character carries a hurtbox approximating their body. Each attack projects a hitbox for its active frames. Overlap means contact, even if the visible weapon appears to miss by a small margin, and a gap means a whiff even when the animation looks close. Most arguments about unfair hits are really arguments about those invisible shapes.
Designers size hitboxes deliberately. Generous hitboxes make attacks feel reliable and satisfying. Tight hitboxes reward precise spacing and create room for skilled evasion. In shooters the same logic applies to headshot boxes and vehicle weak points, and competitive communities measure them closely because a few pixels decide outcomes.
Fighting game players pair hitboxes with frame data to understand a move completely: how large it is, where it reaches, and for how many frames it can connect. Many modern fighting games include an optional hitbox viewer in training mode, which turns guesswork about a loss into something a player can actually study.
In play"His sword looks short, but the hitbox reaches a full step past the blade."