Midair jumping

A midair jump, also known as a double jump, is a movement option in the  series that gives the user a quick boost of vertical speed in midair. While jumping, a character can move left or right, carrying any horizontal momentum they had before the jump. This move is an incredibly important tool for aerial movement, and must be used wisely to ensure that one does not become vulnerable to juggling or edgeguarding.

Normally, a character is only able to jump once in midair. However, in Super Smash Flash 2, several characters can perform more than one midair jump at a time.

Midair jumps in Super Smash Flash
In Super Smash Flash, midair jumps reuse the exact same animations and coding as the characters' first jump. Therefore, technically, the game does not contain midair jumping. This property causes a bug in the game. For instance, if a character who has not jumped becomes airborne, they can use both their jump and their airborne jumps.

Trivia

 * During the time Tails could hover — Beta versions 1.0.0 to 1.0.2 —, his midair jump amount was set to a gigantic amount, due to how the mechanic was coded.