Slab

Slabs are half-versions of their respective blocks.

Obtaining
Stone-type slabs require a pickaxe to mine. Wooden slabs can be mined with anything, but an axe is quickest.

Natural generation
Stone slabs can be found naturally in villages lining the roof of blacksmith shops and inside the Butcher's Shop and the Blacksmith where they form counters. They are also found in strongholds where they are used in some of the stairs, ledges and torch pillars. Sandstone slabs can be found naturally in desert villages, desert wells, and desert temples. Double stone slabs can be found in villages, in the butcher's shop and in blacksmiths. A spruce wood slab serves as a table in igloo basements. Oak, birch, spruce, stone and cobblestone slabs can also be found in woodland mansions.

Placement
Slabs can be placed either right side up or upside-down:
 * Pointing at a block top or the bottom half of a block side will place the slab right side up.
 * Pointing at a block bottom or the top half of a block side will place the slab upside-down.

Slabs cannot be placed on the other four axes.

Behavior


Slabs are treated as a whole block by other blocks and liquids. Two slabs can be piled on top of one another to make a full-size block, but different slab types cannot be mixed in this way.

Redstone can be connected to the wire on the side of the slabs. Redstone placed on top of an upside-down slab can receive signals from an adjacent block of redstone one block lower but cannot transmit signals to it. This is why "ladders" made from upside-down slabs, as pictured to the right, can transmit redstone signals up, but not down.

Mobs see a slab as a full block. Mobs can also spawn on the tops of upside-down slabs and double slabs, but not on lower slabs.

In Bedrock Edition, mobs standing on right-side up slabs fail to pathfind correctly. They seem to perceive the slabs beneath them to be unwalkable, and will often end up spinning around in a small circle when they try to move. The block directly beneath the slab must be air or another right-side up slab to disturb pathfinding.

Due to the way blast rays propagate from an explosion, bottom-half slabs provide extremely effective absorption to explosions directly on top of them.

Sneaking only reduces the player's hitbox height to 1.65 blocks, and so does not allow the player to walk over a single slab with one block of air above it, which is 1.5 blocks of space. A player cannot walk from a block of soul sand directly up to a slab without jumping – this applies not just to soul sand, but to any block $7/8$ of a block high or shorter, because the maximum step height of the player is 0.6 of a block. The player can walk off a slab while sneaking, because the sneaking only prevents falling when the distance is higher than one half block.

If a slab is placed underwater, the empty half of that slab's block will appear and act as air. If the slab is upside-down, not only can the player grab a quick breath of air there, but the player can see as clearly as if they were above the surface.

Minecarts on powered rails will not be repelled from a slab. They will, however, be repelled by a slab with a minecart on top.

Fuel
Wooden slabs can be used as a fuel in furnaces, smelting 0.75 items per slab in the Java Edition and Console editions, and smelting 1.5 items per slab in Bedrock Edition.

Data values
The slab blocks use IDs and data values to differentiate between types. They also have block states which will replace data values in the future.

Double stone slabs

 * Block 43


 * Block 181

The full stone, sandstone, quartz and red sandstone slabs have a top texture on all sides.

Stone slabs

 * Block 44


 * Block 182

Double wooden slabs

 * Block 125

Wooden slabs

 * Block 126

Double stone slabs
minecraft:double_stone_slab

minecraft:double_stone_slab2

minecraft:purpur_double_slab

Stone slabs
minecraft:stone_slab

minecraft:stone_slab2

minecraft:purpur_slab

Double wooden slabs
minecraft:double_wooden_slab

Wooden slabs
minecraft:wooden_slab

Video
Note: This video is outdated, as red sandstone slabs were added in 1.8 and purpur slabs were added to 1.9.

Trivia

 * Slabs let a small amount of light pass through their edges. This light is only visible with Smooth Lighting is turned on, and does not affect mob spawning or other light-dependent processes.
 * The exception of this is that any light directed through a slab does not affect any block's light values north of the source.