A button



The A button is one of the buttons on each controller where it is present. On the Nintendo 64 controller it is blue, on the Nintendo GameCube controller it is an aqua-green, on both the Wii Remote and Classic Controller it is transparent with a white backing, and on both the Nintendo Switch Joy-Con and Pro Controller it is dark gray. The color of the button on the Wii U GamePad and Wii U Pro Controller matches the color of the controller, while it varies on the Nintendo 3DS.

Overview
In the default controller layouts of all installments in the  series, the A button is used mostly for executing standard attacks. This includes Neutral attack, all Tilt attacks, Dash attack, all standard Aerial attacks, all Smash attacks (in conjunction with the control stick), Pummel, Floor attack, Edge attack, and some Command-input moves. Outside of gameplay, the A button is also the standard "confirm" button when navigating menus.

When playing with the Wii Remote held sideways, the 2 button acts as a substitute for the A button, performing smash attacks (when pressed with the D-pad or the 1 button) and confirming selections on menus, whereas the actual A button is used for taunts. When using Joy-Con (R) as a single Joy-Con held horizontally, the A button will become the bottom button, acting like a B button and performing special attacks, while the A button's menu and battle functionalities are given to the X button.

Super Smash Bros. Brawl introduced the controls menu option introduced in this game allows non-default actions to be mapped to the A 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 A button can be used in Ultimate.