Crawling (also known as crouch walking) is a technique introduced in Super Smash Bros. Brawl. While crouching, it allows certain characters to move while staying low to the ground, and can be used to avoid certain projectiles.
The usefulness of crawling primarily depends on how low the character's crouch is. For example, Snake has a very low crouch that significantly reduces his height, making his crawl highly effective for dodging projectiles and attacks with high hitboxes, while Bowser's crouch is much higher and barely reduces his height, leaving it near useless to dodge such attacks. While most characters can change the direction they face while crawling, all crawling characters can crawl backwards.
Characters can use their down tilt attack while crawling. Some characters have down tilts that move them forward, causing them to pseudo-crawl, but the usefulness of this is questionable.
Crawling is not often used in competitive matches, as other methods of approach tend to be more practical. The exception to this are characters with very low crawls (such as the aforementioned Snake) in certain matchups, as their low crawl allows them to approach while being unable to be hit by opposing projectiles, particularly against Falco.
Characters who can crawl
*: These characters can only psuedo-crawl.
Crawl-sliding is an technique in Brawl which allows the player to slide across the ground backwards for a short period of time. This was first discovered by Smashboards member lilscrappy561, who attempted to moonwalk as in Melee by just walking instead of dashing. If done with a Bunny Hood, a character will slide even further, as if they wavedashed. This can only be done with characters that can crawl.
Performing the crawl slide
To do this, the player must tilt the control stick or d-pad so the character will walk. Once the character is walking, the player must then make a half circle in the opposite direction and let go of the analog stick or pad. The character will slide for a short distance unless they are wearing a Bunny Hood, in which case they will go further. It is easiest to do this with Luigi.
Crawl sliding is most often used as a double-cross-up, used more by characters with short jumps. For example, Bowser can crawl-slide behind an opponent who is in front of him while charging his forward smash, so less time is spent vulnerable.