Crawling

Crawling is a feature that allows the player to traverse areas less than one and a half blocks high.

Entering crawling
Crawling can be initiated in any way that causes the player's head to intersect a collidable block in such a way that the area underneath the block is less than 1.5 blocks. For example:


 * Closing a trapdoor on the player
 * Using a piston to push a block into the player's head
 * Using an ender pearl to teleport into a sufficiently small gap
 * Exiting swimming mode in a one-block-high space
 * Exiting elytra mode in a one-block-high space
 * Having a tree grow over a player
 * Having a shulker box push you down

In these circumstances, the player will automatically switch to a crawling state. When enough space opens up above the player's head, the player will automatically exit the crawling state and begin sneaking or standing again.