Hitbox

Hitboxes are the main structure for how attacks are executed in the  series and Fraymakers. They primarily represent areas in which an attack is active, and when an attack's hitbox collides with an object's damageable area (also known as a hurtbox), the attack hits the object. They are present on all interactive elements of the game, such as characters, items, and stage hazards.

Hitboxes are rectangular in shape and are normally hidden from the player. In Super Smash Flash 2, a function exists to make most hitboxes visible during gameplay, though this is intended only for developers and otherwise only accessible through hacking. Fraymakers is planned to allow hitboxes to be visible during Training.

Types of hitboxes in Super Smash Flash 2
There are nineteen types of hitboxes used across Super Smash Flash 2, seven of which become visible when activated with developer controls. This is a list of the hitboxes in the game accompanied by their colors when visible, if applicable, and their functionalities.

Disjointed hitbox
Disjointed hitboxes are attack boxes that are not attached to the normal hitboxes of characters. These types of hitboxes can hit projectiles and other attacks without risking damage to the player. These hitboxes tend to be found on weapons, such as swords. Some of them are long, giving more range to the character's attacks.

Interpolation
Interpolation is the action of giving some parts of a frame hitboxes when they would not normally have them. This can make the colliding hitboxes more accurate. It can be used in the blur of swords or in parts beyond a character's limbs.

Trivia

 * In v0.9b of the SSF2 demo, and, for some reason, had unneeded handboxes in their idle animations.