You can activate sneaking by pressing left shift (default) or center button on Pocket Edition (as of update v0.12.1). Sneaking helps you do a lot of things, such as walking on ledges without falling, not falling when you stop climbing a ladder midway, staring at another player, etc., but is mainly used for concealing the player's username from being visible through blocks. However, when viewed up close, one can see the username.
However, there are negatives: sneaking makes you walk around 1.3 m/s, much slower than the normal 4.3 m/s. As said, walking near ledges without falling can only be done with sneaking, but it is still possible to fall if stepping into a fall of less than 0.5 blocks (like from a block to a slab, or down some stairs).
- By using the F5 Button, viewing yourself in 2nd or 3rd Person View will show that the player is bending over.
- Sleeping in a Bed while also sneaking will show you still sleeping but just able to see your player.
- Sneaking was added in one of the Secret Updates.
- When it was originally added, you could still fall off ledges while doing it.
- It is still possible to go off a ledge by moving to the edge of a block and jumping while on the edge.
- Sneaking in Multiplayer mode will render your nametag invisible to other players that are through walls and are more than 5 blocks away.
- Sneaking also darkens your nametag in Multiplayer mode.
- Sneaking while blocking on Soul Sand over Ice through a Cobweb with the Slowness II effect is the slowest form of movement, at 1 block every 42 seconds.