Block States and Predicates

Details

Block syntax	id[state=value,state=value]{data}. The minecraft: part may be left out. Spaces inside the brackets are allowed.
States	Each state can be set once. States that are left out keep the default value of the block.
Unknown states	A state or value the block does not have is refused, for example minecraft:stone[facing=east].
Block data	Data in { } after the block sets what the block holds, such as the items in a chest or the text on a sign.
Placing commands	The /setblock and /fill commands take one exact block. Tags are refused with "Tags aren't allowed here; only actual blocks are".
Block tests	Used by /execute if block, /fill ... replace and /clone ... filtered. They take a block id or a tag starting with #.
Testing states	Only the states you list are compared. With a tag, a block that does not have a listed state does not match.
Testing data	Only the values you list are compared, and the block must hold data at all.


id	The block in its default state	/setblock 10 64 10 minecraft:stone
id[state=value]	The block with chosen states	/setblock ~ ~ ~ minecraft:oak_stairs[facing=east,half=top]
id{data}	The block with block data	/setblock ~ ~ ~ minecraft:chest{Items:[{Slot:0b,id:"minecraft:diamond",count:1}]}
id[state=value]{data}	States and data together	/setblock ~ ~ ~ minecraft:chest[facing=north]{Items:[{Slot:0b,id:"minecraft:diamond",count:1}]}


id	That block in any state	/execute if block ~ ~-1 ~ minecraft:grass_block run say on grass
#tag	Any block in the tag	/execute if block ~ ~-1 ~ #minecraft:logs run say on a log
id[state=value]	That block with the listed states	/execute if block ~ ~ ~ minecraft:oak_stairs[half=top] run say upside down
#tag[state=value]	Any block in the tag with the listed states	/execute if block ~ ~ ~ #minecraft:stairs[facing=east] run say facing east

id{data}	That block holding the listed data	/execute if block ~ ~ ~ minecraft:chest{Items:[{id:"minecraft:diamond"}]} run say has diamonds
#tag{data}	Any block in the tag holding the listed data	/execute if block ~ ~ ~ #minecraft:signs{is_waxed:1b} run say waxed


execute if block	Runs the rest only if the block matches	/execute if block ~ ~-1 ~ #minecraft:logs run say on a log
execute unless block	Runs the rest only if the block does not match	/execute unless block ~ ~ ~ minecraft:air run say solid
fill ... replace	Replaces only the matching blocks in the area	/fill ~-5 ~ ~-5 ~5 ~ ~5 minecraft:air replace #minecraft:leaves
clone ... filtered	Copies only the matching blocks	/clone 0 64 0 10 70 10 20 64 0 filtered #minecraft:wool move

/setblock ~ ~ ~ minecraft:oak_stairs[facing=east,half=top]

Places upside-down oak stairs facing east.

/setblock ~ ~ ~ minecraft:chest[facing=north]{Items:[{Slot:0b,id:"minecraft:diamond",count:1}]}

Places a chest facing north with one diamond in its first slot.

/fill ~-5 ~ ~-5 ~5 ~ ~5 minecraft:stone replace minecraft:dirt

Turns dirt into stone in an 11 by 11 square at your height.

/fill ~-5 ~ ~-5 ~5 ~ ~5 minecraft:oak_slab[type=top] replace minecraft:oak_slab[type=bottom]

Turns bottom oak slabs into top slabs in the area.

/clone 0 64 0 10 70 10 20 64 0 filtered minecraft:stone

Copies only the stone blocks of the area to the new spot.

/execute if block ~ ~ ~ #minecraft:stairs[facing=east] run say facing east

Says the text if you stand in any stairs block that faces east.