B button


 * For the Japanese smasher, 

The B button is either the large, green button on the Nintendo 64 controller, the small, red button on the Nintendo GameCube controller, the rectangular trigger button on the back of the Wii Remote, the clear button towards the bottom right of the Classic Controller, the circular button on the Wii U GamePad, Wii U Pro Controller and Nintendo 3DS (varies in color on 3DS, matches the color of the Wii Remote, Wii U GamePad and Wii U Pro Controller), or the bottom dark gray face button on the Nintendo Switch's right Joy-Con and Pro Controller.

Overview
In the default controller layouts of all installments in the  series, the B button is used mostly for executing special attacks. This includes Neutral special, Side special, Up special, Down special, Final Smash and some Command-input moves. Outside of gameplay, the B button is also the standard "back" button when navigating menus.

When playing with the Wii Remote held sideways, the 1 button acts as a substitute for the B button, performing special moves, whereas the actual B button is used to shield the character with default controls. When using Joy-Con (R) as a single Joy-Con held horizontally, the B button will become the left button, acting like a Y button and performing jumps, while the B button's menu and battle functionalities are given to the A button.

Super Smash Bros. Brawl introduced the controls menu option introduced in this game allows non-default actions to be mapped to the B button. This option has returned in every subsequant Smash release. While not directly related, Nintendo Switch hardware version 10.0.0 introduced the ability to map the functionality of any button to any other button from the console options menu, further diversifying how the B button can be used in Ultimate.