Java Edition 21w38a

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21w38a is the second snapshot for Java Edition 1.18, released on September 23, 2021,^[2] which make more performance-related tweaks, reimplements telemetry, and fixes bugs, mostly relating to terrain changes that were accidentally removed in the previous snapshot.

Any worlds from previous versions cannot be opened in this version.

Languages

• Added Lombard.^{[note 1]}
• Added Toki Pona.^{[note 2]}

Options

• Added "Simulation Distance" video setting, a new slider.
  • Entities aren't updated outside of simulation distance.
  • Allows higher render distance with less CPU load.

Subtitles

• Added a new subtitle for the crop sound of shears.

server.properties

• Added simulation-distance.

Telemetry

• 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. ^[3]

Ore distribution

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

Performance

• 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.

Sprinting

• 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.

• Unlike most of the first-of-the-week snapshots, this was released on a Thursday instead of Wednesday, similar to the snapshots before 14w26a.