Slowness

Slowness decreases walking speed.

Effect
Slowness decreases walking speed by 15% × level; it will contract the player's field of view accordingly. Negative levels of Slowness will increase walking speed. However, jump-sprinting will be barely affected.

Unaffected mobs
Boss mobs are immune to the Speed effect. While not immune, flying mobs are unaffected by the Speed effect. Shulkers are also unaffected by, though not immune to, Slowness.