The Spring Jump (スプリングジャンプ Supuringujanpu?) is Sonic's up special move in Super Smash Bros. Brawl and Super Smash Bros. for Nintendo 3DS / Wii U, which acts as a personalized spring, causing a spring to immediately appear underneath him, shooting Sonic up a great vertical distance.
When used on the ground, the spring remains in place for a while, allowing other characters to use it, too. If this move is used in the air, the spring falls downwards, acting as a projectile that deals 4% damage and horizontal knockback, making it effective for edge guarding. After using this move, Sonic still retains the ability to use normal aerial attacks and air dodges, but will be unable to use special moves until he touches the ground. Additionally, this move does not allow Sonic to grab any ledges onstage (i.e. auto-sweet spot) until he is finished gaining vertical distance, making it dangerous for recovery if Sonic goes above a ledge and exposed to an edge-guarder. Barring any outside influence, the spring will remain on the ground long enough for Sonic to do three jumps off of, disappearing just as he makes his third jump.
If Sonic bounces off a previously set Spring, it doesn't count as his third jump as long as he doesn't land on it immediately from his up special, so he can use Spring Jump immediately afterward, gaining a great deal of height, essentially two back-to-back up specials.