Bucket

Buckets are tools used to carry water, lava, milk, powder snow, live fish (cod, pufferfish, salmon, and tropical fish), and axolotls.

Usage
Empty buckets can be used to "pick up" a water or lava source block by pressing item on a block of the relevant type. If the empty bucket is part of a stack and the player's inventory is full, the filled bucket drops in front of the player as an item.

A bucket filled with a source block can then be used to place its source block contents in the empty block next to the side of the block the player is currently looking at, or replacing the block looked at for some replaceable blocks.

One can press when looking at a cow, mooshroom, or goat to fill a bucket with milk. A bucket full of milk can be emptied only by drinking it or by using it in crafting a recipe (like cake).

A bucket full of water can be used on a live aquatic mob (cod, salmon, tropical fish, pufferfish, axolotl or tadpole) to collect the mob in the bucket for transportation to another location. The mob in item form becomes a bucket of aquatic mob.

An empty bucket can be used to empty a cauldron with water or lava, filling the bucket with the fluid. This does not work with dispensers.

A lava bucket placed in the fuel slot of a furnace becomes an empty bucket after the lava is consumed during smelting.

An empty bucket fills with water when placed in the fuel slot of a furnace while smelting a wet sponge.

An empty bucket can be used to collect powder snow, filling the bucket with powder snow. Emptying the powder snow bucket places the powder snow block in the empty block next to the side of the block the player is currently looking at.

ID