Jump Boost

Jump Boost is a status effect that primarily increases the jump height of the player.

Mechanics
Jump Boost allows the player to jump higher than the normal $1 1/4$ blocks. Jump Boost I increases the player's jumping height to $1 15/16$ blocks, and Jump Boost II increases it to $2 1/2$ blocks. It also reduces fall damage by each level. Negative levels decrease jump height and increase fall damage (which also causes the player to start taking damage from short falls that would normally do no damage); extreme negative levels eliminates all jumping ability and causes damage even when stepping off a slab.

Unaffected mobs
Slimes and Magma Cubes are unaffected by Jump Boost.