Minecraft wiki entry for Cobweb, associated text: All mobs except for spiders and cave spiders experience slow movement through a cobweb. A mob falling through a cobweb takes 13 seconds to move down 1 block. A cobweb can partially stop blast damage if a player and the entity causing the explosion are both caught in the cobweb. The slowing effect of the cobweb increases if it is placed on ice. The slowest a player can move in vanilla Minecraft without commands or other third-party tools is by placing cobwebs on Blue Ice, sneaking, drinking a level IV Turtle Master Potion, and blocking, which causes the player come to a near-total standstill, moving only a single block every few minutes.