Crouch

The crouch or duck move has been used in almost every Mario platformer. To use it, the player must simply press in 2D games, or  /  /  /  /  /  /  /  in 3D games. If the player releases the button, characters return to their standing position. It is used to duck under projectiles and slide under walls while moving. Crouching in midair has the player perform a Ground Pound instead (except while riding Yoshi in Super Mario Galaxy 2 or capturing an object/enemy in Super Mario Odyssey).

Jumping while crouching in 3D games lets the player do a Backwards Somersault in place or Long Jump while dashing; Super Mario Sunshine is an exception, as Mario can perform a Backwards Somersault, but he cannot crouch or Long Jump.

If characters jump while crouching in 2D games, Super Mario 3D Land, Super Mario 3D World, and Super Mario 3D World + Bowser's Fury, they can jump while still crouching. This can be utilized to get into one-block tall holes. It can also be used within these tunnels to move slightly with each jump, but if the player releases the crouch button, the character performing it will automatically go towards the opposite direction they are facing. Small characters can only crouch in Super Mario Bros. 2, Super Mario World, the New Super Mario Bros. games, Super Mario 3D Land, Super Mario 3D World, Super Mario Maker (in the Super Mario World and New Super Mario Bros. U styles only), and Super Mario Maker 2.

In Super Mario Bros. 2, crouching for a small period of time will charge up characters so they can jump higher (once per charge). This ability is called the Power Squat Jump. The Backwards Somersault in Super Mario 3D Land, Super Mario 3D World, and the respective style in Super Mario Maker 2 operates similarly to this. This jump itself can be used in SMB2 form in the Super Mario Bros. style in Super Mario Maker 2.

In most 3D games, such as Super Mario 64, and games in the Super Smash Bros. series since Super Smash Bros. Brawl, attempting to move while in a crouch allows the character to crawl, which allows Mario to scale steep slopes and walk carefully on sloped surfaces. Only a number of characters in the Super Smash Bros. series can do this. In Super Mario 3D Land, Super Mario 3D World, and Super Mario Odyssey, the characters can also roll while crouching (by attacking while crouching), while in Super Mario 64 and its remake, Mario (and Luigi, Yoshi, and Wario in the DS version) use Sweep and Slide Kicks instead.

Super Mario Bros. 3

 * Wii Virtual Console manual description: "Press down on to crouch. You can also press down on  to slide down slopes (except when wearing the Frog Suit)."

Super Mario Land

 * Virtual Console manual description: "Press when you are Super Mario or Superball Mario to crouch down."

Super Mario 3D Land

 * North American website bio: "This lets Mario stay low and fit into tight spaces. He can move while crouching too."
 * European website bio: "Hold down the L Button (or the R Button) to crouch. You can move around while crouching - great for when you need to squeeze through a tight space."