The Caves & Cliffs Prototype Data Pack is an official data pack that was released periodically by Mojang Studios from April 2021 to May 2021. It contains several experimental and work-in-progress features, most of which were eventually released in Java Edition 1.18. Its first release coincided with the announcement that Caves & Cliffs would be split into two major updates. The data pack was eventually superseded by experimental snapshots as changes that are too large for a data pack were introduced.
Spaghetti caves are long, thin caves that have small aquifers and are more similar to original caves.
Noodle caves are thinner, squigglier, and more claustrophobic variants of spaghetti caves.
Contain aquifers, bodies of water with different heights, independent of sea level (Y=63).
Only used below Y=31, meaning any noise caves between Y=31 and Y=63 are flooded with water.
Aquifers below Y=0 sometimes generate with lava instead of water.
The original carvers still exist with their generation slightly tweaked to add more variation and to better blend in with noise caves.
New crevice carvers, which are deep, long cracks in the ground that are thinner and straighter than canyons.
Ore veins, long and rare formations of ore and rock, have been introduced.
Changed the generation of all ores, making them have a spread value like lapis lazuli ore. Some still retain a linear generation alongside a spread generation.
Copper ore generates between Y=0 and Y=96, and uses spread like all other ores. It peaks at Y=48.
Emerald ore generates above Y=32 as a spread, peaking at Y=256 and decreasing in quantity as the altitude decreases.
Coal ore attempts to generate twice: once, evenly between an altitude of Y=136 and Y=256; and as a spread, peaking at an altitude of Y=96 and generating between an altitude of Y=0 and Y=192.
Iron ore attempts to generate three times: once as a spread peaking at an altitude of Y=256, generating above Y=128; another as a spread peaking at Y=16 and generating with a minimum height of Y=-24 and a maximum height of Y=57, and a smaller one spreading evenly between the altitudes of Y=-64 and Y=64.
Gold ore generates between the altitudes of Y=-64 and Y=32, peaking at Y=-16. The extra gold that generates in the badlands biome was left untouched.
Lapis lazuli ore attempts to generate twice: once, as a spread between the altitudes of Y=32 and Y=-32, peaking at an altitude of 0; and evenly between the altitudes of Y=64 and Y=-64, generating buried like ancient debris.
Redstone ore attempts to generate twice: once, evenly between an altitude of Y=15 and Y=-64; and as a spread, peaking at an altitude of -64 and generating below an altitude of Y=-32.
Diamond ore generates below Y=16 as a spread, peaking at Y=-64 and decreasing in quantity as the altitude increases.