ZL button

The ZL button refers to one of two circular buttons on the top of the Classic Controller and New Nintendo 3DS and the button above the L button on the Wii U GamePad, Wii U Pro Controller, Nintendo Switch Pro Controller and left Joy-Con. The ZL button matches the color of the Classic Controller, Wii U Pro Controller and Wii U GamePad, while they are dark gray on the Joy-Cons and Switch Pro Controller.

Overview
The ZL button initially functioned identically to the Z button, which is to activate a grab, in Super Smash Bros. Brawl,, and for as of version 1.0.5. Super Smash Bros. Ultimate changed its functionality by instead making it activate a shield instead while grab was moved to the L button and R button.

When using a single Joy-Con in Super Smash Bros. Ultimate, the ZL or ZR button (depending on which Joy-Con is used) is not set to any action by default. Instead, the SL button is used for grabbing and the SR button is used for shielding. In this configuration, the L, R, ZL and ZR buttons cannot be set to grab.

In Brawl, For Wii U, and Ultimate, ZL can be customized in the Controls to perform other functions, while in For 3DS, ZL is coded to do the same functions as the R button, as the game was released before the New Nintendo 3DS introduced a ZL button to the system. Prior to version 1.0.5 of the game, this button's functions were reversed, so ZL would trigger the same actions as L, though their functions outside of battle (such as in menus) were the same as in current versions. On the character selection screen in Smash 3DS, the ZL and ZR buttons are also used to scan amiibo to the lower screen and register them for battles. 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 ZL button can be used in Ultimate.