An up smash (abbreviated u-smash) (上スマッシュ攻撃, Up/upper/above smash attack) is a smash attack performed by any character by tapping the control stick upward and pressing A, or, outside of Melee's single player modes, by pressing up on the C-Stick.
Since Super Smash Bros. Melee, all smash attacks can be charged by holding down the A button for up to one second, multiplying damage and knockback by up to 1.4. In Ultimate, with some exceptions, these charges can be held for up to 3 seconds (or 180 frames), but the attack stops increasing in strength after the 1-second mark.
Up smashes generally follow several trends: they usually send opponents vertically upwards, which give them consistent KO potential on most neutral stages (such as Battlefield). They also tend to cover directly above the user, either through a wide sweeping motion with average knockback (such as Mario and Pikachu), or an upward thrust with a stronger and smaller hitbox (with some possessing grounded hitboxes to lead into the main hit, such as Marth and Steve). Prior to Ultimate, up smashes were also one of the few attacks that could be jump-canceled, enabling them to be used out of shield immediately and during any part of a character's dash animation, except the skidding animation when they stop running. As a result, some fighters have up smashes that serve as excellent out of shield punishes, while others function as precise, but powerful anti-airs.
From Brawl onwards, jump-canceling to perform a running up smash is unnecessary, and the turn-around animation can be jump-canceled into a reversed up smash. In Ultimate, jump-canceling is not required for up smashes out of shield, and can now be done instantly; additionally, all grounded moves can be canceled from a dash, which lower the utility of some out of shield up smashes.
List of up smashes
Notable up smashes
Fox's up smash in Melee is known as the best grounded KO move in the game, due to high power and extremely fast startup; the hitbox comes out on frame 7, making Fox's up smash as fast as his grab.