On April 14, 2021, Mojang Studios announced that the update would be split into two updates due to the amount and complexity of content, as well as team health.[3] Multiple features such as revamped mountain and cave generation, the lush caves and dripstone caves biomes, and increased world height were removed on 21w15a, and were subequently released in 1.18.[4] A data pack was included in the Minecraft.net article for 21w15a that re-enabled the removed features, and subsequent snapshots updated this data pack.
1.17, the first release of Caves & Cliffs: Part I, is a major update to Java Edition announced at Minecraft Live 2020[1] and released on June 8, 2021.[2]
On April 14, 2021, Mojang Studios announced that the update would be split into two updates due to the amount and complexity of content, as well as team health.[3] Multiple features such as revamped mountain and cave generation, the lush caves and dripstone caves biomes, and increased world height were removed on 21w15a, and were subequently released in 1.18.[4] A data pack was included in the Minecraft.net article for 21w15a that re-enabled the removed features, and subsequent snapshots updated this data pack.
Notable additions
Source : Minecraft Wiki