Minecraft Wiki
Minecraft 21w38a
Java Edition 21w38a.png

Java Edition



Release date

September 23, 2021

Snapshot for



Client (.json)

Obfuscation maps


Protocol version

 dec: 1073741866
 hex: 4000002A

Data version


21w38a is the second snapshot for Java Edition 1.18, released on September 23, 2021,[1] which make more performance-related tweaks, reimplements telemetry, and fixes bugs, mostly relating to terrain changes that were accidentally removed in the previous snapshot.



  • Added "Simulation Distance" video setting, a new slider.
    • Entities will not be updated outside of simulation distance.
    • Allows higher render distance with less CPU load.
  • Added a new subtitle for the crop sound of shears.
  • Added simulation-distance.
  • Readded, previously a part of game known as "snooper" until 18w20c.
    • Only implemented in world load event now.
    • Sent data when loading singleplayer world or connecting to multiplayer server.
    • Contains following information:
      • Launcher identifier
      • User identitifer (XUID)
      • Client session ID (changes on restart)
      • World session ID (changes per world load, to be reused for later events)
      • Game version
      • Operating system name and version
      • Java runtime version
      • If client or server is modded (same information as on crash logs)
      • Server type (single player, Realms or other)
      • Game mode
    • Cannot be disabled. [2]


World generation[]

Ore distribution
  • Copper ore now generates up to Y=95, and increased its amount.
  • Lapis lazuli ore now generates in blobs, like other ores, instead of spread out.


  • Now, various background tasks including world generation are executed on a background thread pool.
    • The size of the thread pool equals Amount of available CPU threads - 1.
      • Maximum amount of threads is 255, instead of 7. This limit can be overridden by Java system property max.bg.threads.
  • No longer reduced to walking when touching the wall at low angles.


21 issues fixed
From released versions before 1.18
  • MC-44055 – Game fails to switch the audio output from one device to another from the title screen after the game has started.
  • MC-128762 – Strongholds do not generate in ocean buffet worlds.
  • MC-136288 – Strongholds don't generate in swamp biomes.
  • MC-158410 – Strongholds don't generate in beach surface and snowy beaches buffet worlds.
  • MC-183184 – Sprinting stops as soon as you touch another block.
  • MC-202036 – Adding a biome to a datapack shifts biome IDs in existing chunks.
From the previous development version
  • MC-236611 – No sound for using shears on weeping, twisting, cave vines or kelp.
  • MC-236618 – Strongholds don't generate in 21w37a.
  • MC-236621 – Liquids sometimes do not propagate.
  • MC-236633 – Random light level of 0 in sky.
  • MC-236656 – Crash when changing render distance: java.lang.ArrayIndexOutOfBoundsException: Index 28084 out of bounds for length 26136.
  • MC-236665 – Memory leak in 21w37a.
  • MC-236682 – Large and continuous lag spikes sometimes occur when loading or reloading into a world in 21w37a.
  • MC-236698 – Big spruce trees don't generate in groves.
  • MC-236711 – Starting and stopping JFR profiling multiple times within the same minute overwrites previous JFR results saved during that minute.
  • MC-236718 – Dripstone caves generate above the ground.
  • MC-236753 – Caves and lakes generating too much in desert surface.
  • MC-236795 – Cannot start with alternate JVM due to JFR requirement.
  • MC-236873 – Problems with JFR event metadata.
  • MC-236967 – Too many aquifers on biome surfaces at Y=63 and below.
  • MC-237109 – Aquifers often generate with harsh straight borders.


Videos made by slicedlime:


  • Unlike most of the first-of-the-week snapshots, this was released on a Thursday instead of Wednesday, similar to the snapshots before 14w26a.
  • Worlds from previous versions cannot be opened in this version.


  1. "Minecraft Snapshot 21w38a" – Minecraft.net, September 23, 2021
  2. MC-237493 – resolved as "Works As Intended"


  1. Also available for versions since 19w34a.
  2. Also available for versions since 20w45a.