Minecraft Wiki
Minecraft 21w39a
Java Edition 21w39a.png

Java Edition



Release date

September 29, 2021

Snapshot for



Client (.json)

Obfuscation maps


Protocol version

 dec: 1073741867
 hex: 4000002B

Data version


21w39a is the third snapshot for Java Edition 1.18, released on September 29, 2021,[1] which add new advancements and fixes bugs.

Starting from this snapshot, players can open old worlds again.



  • Added four new advancements:
    • Caves & Cliffs
      • Fall from the top to the bottom of the Overworld
    • Feels like home
      • Ride a strider on lava for 50 blocks in the Overworld
    • Star Trader
      • Trade with a villager at the build height limit
    • Sound of Music
  • Added new advancement triggers.
    • fall_from_height
      • Triggered when a player lands after falling.
    • ride_entity_in_lava
      • Triggered for every tick when player rides in lava.


Loot tables
  • Added new loot table function set_potion, to set Potion tag on any item.
    • Has following parameters:
      • id: Potion ID



  • Now can spawn in aquifers inside dripstone caves.
  • No longer spawns in dripstone caves.

World generation[]

Lofty Peaks, Snowcapped Peaks and Stony Peaks
  • Its small mountains are more jagged now.
  • Trees in Meadows now always contain a bee nest.


  • "Light as a Rabbit" now has "Sweet Dreams" as its parent instead of "Adventure".


Buried Treasure
  • Buried treasure chests can now contain water breathing potions.
Chunk format
  • Chunk’s Level.Sections[].BlockStates & Level.Sections[].Palette have moved to a container structure in Level.Sections[].block_states.
  • Chunk’s Level.Biomes are now paletted and live in a similar container structure in Level.Sections[].biomes.
  • Chunk’s Level.CarvingMasks[] is now long[] instead of byte[].
  • Redesigned how effects look in the inventory screen.
    • Can display while recipe book is showing.
    • The list of effects are now shown to the right of the player's inventory, instead of the left side.
    • When the inventory effects list is visible, it will be hidden from the game view to reduce screen clutter.
    • There’s now two modes of seeing the effect list: compact and classic:
      • Classic is the pre-existing list of effects, one after another.
      • Compact is a single icon for each effect, suitable for small screen estate.
      • The game will automatically switch between the two looks to suit the available screen estate.
  • Changed default brightness to 50.
Resource packs
  • Resource pack version number is now 8, as the following has been changed:
    • inventory.png now contains an extra sprite for a thin-layout version of the effect list in the inventory.
  • server.jar now bundles individual libraries instead of merging all the files into single archive.
    • This change is meant to solve certain problems related to Java modules.
  • On startup, server.jar will unpack libraries into a directory configured by bundlerRepoDir (default: working directory).
    • To run different main class than server, use bundlerMainClass property.


14 issues fixed
From released versions before 1.18
  • MC-116359 – Status effects aren't displayed in inventory when recipe book is open.
  • MC-129485 – Certain biome specific plant distribution is completely based on chunks, causing patchy biome generation.
  • MC-145376 – Bamboo could generate underground when generating in non-bamboo jungles.
  • MC-149822 – Bottom border on status effect displays in the inventory is missing.
  • MC-193348 – Status effect bars shift the player's inventory in creative mode.
  • MC-196723 – Potion effects obtained in creative mode while in inventory do not show up until reopening inventory.
  • MC-214894 – Bamboo generates in caves under jungles.
  • MC-214959 – Sugar cane generated in cave.
  • MC-218167 – Chatting causes lag to occur.
From the 1.18 development versions
  • MC-236755 – "Feature Placement" crash: java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0.
  • MC-236903 – Naturally generated cave vines have an age between 17-25.
From the previous development version
  • MC-237464 – Packet sent event is recorded as packet received event.
  • MC-237505 – Certain Biome Builder debug values do not change.
  • Removed generic snapshot tooltips from incompatible worlds (except for worlds created in experimental snapshots).


Videos made by slicedlime:


  1. "Minecraft Snapshot 21w39a" – Minecraft.net, September 29, 2021