Java Edition 1.18

1.18, the second release of Caves & Cliffs, is an upcoming major update to  set to release in late 2021. It was first announced alongside the release of 1.17 snapshot 21w15a when Mojang stated the Caves & Cliffs update would be split in two. The official datapack for previewing the world generation changes in the latest snapshot can be found here and will be regularly updated alongside 1.17 snapshots.

World generation

 * Mountains


 * Height dependent generation.
 * Revamped, featuring some new small spruce trees on the slopes and ice and packed ice above the peaks.
 * Contain goats, rabbits, snow blocks, snow layers and powder snow.
 * Iron ore, emerald ore and coal ore are found in abundance.
 * Emerald ore no longer generates in veins of only one.
 * Can generate up to Y=256.
 * New sub biomes.


 * Caves


 * Completely overhauled.
 * Now stretch down to Y=-59.
 * The cavern now generates in 2 layers of different stone bases depending on the depth.
 * Cavern layer above Y = 0 is made up of regular stone.
 * Stone transitions to deepslate from Y=0 to Y=-7.
 * Deepslate now completely replaces stone from Y=-8 to bedrock.
 * Certain types of ores and structures still generate in the deepslate layer, as well as tuff.
 * Dirt, diorite, granite and andesite do not generate in this layer.
 * Biomes inside of caves introduced such as dripstone caves.
 * Contain aquifers, bodies of water with different heights, independent of sea level (Y=63).
 * Aquifers below Y=0 sometimes generate with lava instead of water.
 * Improved old caves to blend in with the new generations of caves better.
 * New carver called crack carver, which appears as a fissure on the ground, like ravines but narrower and can go very deep.
 * New noise caves, coming in 2 forms, cheese and spaghetti.
 * The original caves still exist, mixing with the noise caves.
 * Cheese caves have large stone towers stretching from the bottom of the cave to the top.
 * Very large, often large enough to fly with an elytra.
 * Abundant with aquifers and ores.
 * Spaghetti caves are long, thin caves that have small aquifers and are more similar to original caves.


 * Ore veins


 * Large, rare, snake-like ore formations.
 * Copper ore veins mixed with granite generate above Y=0.
 * Iron ore veins mixed with tuff generate below Y=0.

Biomes

 * Deep dark biome


 * New biome at the "deepest depths of the world".
 * Wardens can spawn here.
 * Contains sculk blocks and sculk sensors.
 * Contains deepslate.
 * Likely generates within the deepslate layer between Y=-1 and Y=-64.
 * May contain candles.


 * Dripstone Caves




 * Contains pointed dripstone (both stalactites and stalagmites) and dripstone blocks.


 * Lush Caves




 * Contain moss, moss carpet, spore blossom, glow berry vines, big dripleaf, small dripleaf.
 * Moss covers the ceilings and floors.
 * Axolotls can spawn here.
 * Clay pools generate inside.


 * Mountains


 * Come in 5 sub-biomes:
 * Mountain Meadow
 * The lowest layer of a mountain.
 * Contain flowers and sweet berry bushes.
 * Mountain Grove
 * The second lowest layer of a mountain.
 * Covered in snow, snow blocks and powder snow, and is filled with spruce trees.
 * Rabbits spawn in this biome.
 * Snowy Slopes
 * The second highest layer of a mountain.
 * Covered in snow, snow blocks, powder snow and ice.
 * Goats spawn only in this biome.
 * Lofty Peaks
 * The highest layer of a mountain, and will only generate if the mountain is high enough.
 * Generates if the surrounding biomes are too warm for snow capped peaks.
 * Covered in snow and ice.
 * Snow Capped Peaks
 * The highest layer of a mountain, and will only generate if the mountain is high enough.
 * Generates if the surrounding biomes are too cold for lofty peaks.
 * Covered in snow, snow blocks, powder snow, ice and packed ice.

Gameplay



 * While in the deep dark cave biome, the ambient lighting occasionally dims temporarily, limiting the player's visibility. This serves as a warning that the warden is nearby.

World generation

 * More extreme and smooth terrain.
 * Likely change to the generation of alternate stone types, to make them appear in larger but less numerous deposits.
 * Possibly seen in a screenshot tweeted by Henrik Kniberg, in which diorite appears to generate in a long and flat horizontal strip, rather than a small unevenly shaped patch.
 * Ore generation has further rebalancing and influences the surrounding stone.21w10a approximate ore distribution.jpg]]


 * Fossils


 * The fossils in the deepest part of the underground generate with Deepslate Diamond Ore instead of Coal Ore.


 * Strongholds


 * Try to generate fully encased in stone, or deepslate at low y-levels.

World generation

 * Mesh caves


 * Seems to be possibly a large tunnel-like cave generation.
 * Not much is known about this cave variation yet, but it was confirmed on Twitter by Henrik Kniberg.
 * Possibly contain "catacomb" style branching cave sections.
 * May be a scrapped idea.

Structures

 * Underground Cabin


 * Seen in the Deep Dark biome during the Minecraft Live 2020 stream.
 * Consists of a chamber with a cobblestone floor and stripped log support beams, containing 3 barrels, a blast furnace, and a large chest, with cobwebs and candles in and around it.
 * May possibly not be a generated structure, but instead a construction built for the purpose of the Warden showcase.

Trivia

 * This is the first major update for Java Edition that is split into two updates since Adventure Update in 2011.