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Minecraft 21w10a
Java Edition 21w10a.png

Java Edition



Release date

March 10, 2021

Snapshot for



Client (.json)

Obfuscation maps


Protocol version

 dec: 1073741842
 hex: 40000012

Data version


21w10a is the thirteenth snapshot for Java Edition 1.17, released on March 10, 2021,[1] which adds lush caves and new deepslate variants.



Cracked Deepslate Bricks
  • A cracked variation of deepslate bricks.
  • Obtained by smelting deepslate bricks.
Cracked Deepslate Tiles
  • A cracked variation of deepslate tiles.
  • Obtained by smelting deepslate tiles.
Deepslate Ore
  • Added deepslate ore variants for copper, emerald and coal ore.
    • Do not generate by default; they only have been added for use by creators of maps and data packs.
    • Like other deepslate ores, they can be used in blasting and smelting recipes like normal ores.
      • Again, like other deepslate ores, they will unlock these recipes in the recipe book.
Infested Deepslate
  • An infested variant of deepslate.

World generation[]

Azalea Tree
Lush Caves biome
  • Currently the biome is only accessible in single-biome worlds.
  • Adaptive to the environment: every type of cave generation can be a lush cave.
  • Moss covers the floors and ceilings, along with moss carpets and grass on the floors.
  • Spore Blossoms grow from the ceiling and drip particles.
  • Contains clay pools where dripleaf plants grow out of them.
    • Clay pools will sometimes generate water sources over air, and the water is suspended and does not flow. This has yet to be fixed.
  • Contains azalea bushes (both variants).
  • Cave vines with glow berries grow from the ceiling and light up the caves.


  • Are now included for all supported render states.
  • Any shader except for the blit shader can also be replaced in resource packs.
  • For now replacing these shaders is not officially supported and the way it works may change in the future.
  • Current rendering engine uses a system similar to the post processing shader pipeline. There are some differences between both system that cater to the slightly different requirements.
  • Added the coal_ores, copper_ores, and emerald_ores block and item tags.
    • Contain both the normal and deepslate ores of each ore type.
  • Added the lush_ground_replaceable block tag.



Deepslate diamond ore, deepslate gold ore, deepslate iron ore, deepslate lapis lazuli ore, deepslate redstone ore, coal ore, diamond ore, iron ore, gold ore
  • The textures of these ores have been changed.
    • Iron ore and deepslate iron ore no longer have streaks, better matching the appearance of other ores.
    • Diamond ore closer resembles deepslate diamond ore.
Cobbled Deepslate
  • The texture has been changed.
  • Can now be smelted back into deepslate.
  • Both the top and sides textures have been changed.
  • Deepslate can now be placed along any axis.
  • Textures in caves now generate with a random rotation.
Deepslate Bricks and Deepslate Tiles
  • Can now be crafted.
Lightning Rod
  • Changelog states they can now be waterlogged, though this is not the case.
Moss Block
  • Using bone meal on it now spreads moss to blocks on any height.


  • The item model has been changed back to a dedicated texture.
    • Similar to tridents, the spyglass still uses a 3d model in the hand.
    • The texture is different from the original item texture.


  • The maximum size that slimes can be summoned with is now 128.

World generation[]

Crack carvers
  • Now are much less common.
  • The fossils in the deepest part of the underground generate with Deepslate Diamond Ore instead of Coal Ore.

The new ore generation for 21w10a.

Ore distribution
  • Now generates more emerald ore in mountains.
  • Now generates more lapis lazuli ore.
  • Now generates less copper ore, gold ore, and redstone ore.
  • Now generates smaller diamond ore blobs, but slightly more frequent (less diamond ore overall though).
  • Now generates less iron ore, and it generates lower down.
    • The deepest iron generation range: previously Y = -64 to -8, now Y = -64 to -32.
    • The middle iron generation range: previously Y = -16 to 80(most at 32), now Y = -24 to 56(most at 16).
  • Reduced air exposure for coal ore.

Command format[]

  • The give command can only give up to 100 stacks of items at a time (e.g. 6400 stone or 100 iron swords)
  • Can no longer set a player's spawnpoint to areas that are out of the world.


  • Glowing is now based on the outline of all layers on an entity, not just the base layer.


Game library updates
  • Rendering is now using OpenGL 3.2 core profile.
    • All fixed function rendering has been replaced with shader based rendering.
  • Changed the splash "OpenGL 2.1 (if supported)!" to "Now on OpenGL 3.2 core profile!"
  • Glow item frames have their own subtitles, no longer using the same subtitles as normal item frames.
  • Removed moss block, the #flowers block tag, grass, tall grass, moss carpet, small dripleaf, big dripleaf, big dripleaf stem, and vines from the lush_plants_replaceable block tag.
  • Removed the azalea_log_replaceable block tag.


54 issues fixed
From released versions before 1.17
  • MC-29318 – Client misses inventory updates while player is manipulating items - causes invisible items.
  • MC-32452 – Fog generates only in the centre of the screen.
  • MC-84121 – Shape of glow effect is based on mob's base layer.
  • MC-87019 – Only visible slots are updated clientside when you are inside an inventory.
  • MC-93243 – Fog Rendering On AMD Graphics Cards & Integrated Graphics.
  • MC-124109 – Horses glitched with glowing effect.
  • MC-135561 – Failed to create OpenGL context on some Linux systems with Nvidia driver.
  • MC-148071 – If you switch to a crossbow after charging another bow/crossbow, the crossbow you switched to will go weird for a second in the hotbar.
  • MC-148206 – Hand punching animation is played after eating crops while looking at a block.
  • MC-154094 – Lectern running /clear turns items into ghost items.
  • MC-165208 – Text and other UI elements are completely black when being affected by night vision and the void/blindness simultaneously.
  • MC-175964 – Setblock command run by book in lectern to clear inventory run in command block causes ghost items.
  • MC-182455 – Entity shadow texture glitching with resource pack.
  • MC-186864 – Leather armour can appear white.
  • MC-194675 – While spectating a creeper, enderman, spider or cave spider, UI elements are rendered completely white.
  • MC-201316 – The /give command can create so many items that the game will freeze.
  • MC-210408/spawnpoint allows players to set their spawnpoint to out-of-bounds coordinates, which crashes the game when trying to respawn.
  • MC-214629 – FOV decreases when underwater regardless of FOV Effects accessibility setting.
  • MC-215534 – Spectating a mob with a shader whilst having a carved pumpkin equipped turns the screen completely white.
  • MC-216510 – The world border red effect, affects the brightness of a mob's shader.
From the 1.17 development versions
  • MC-204782 – The glowing effect outline no longer renders (Intel Graphics on macOS).
  • MC-205112 – Enchantment glint appears white while inside powder snow.
  • MC-206628 – Emptied Bundles have an empty Item Tag.
  • MC-207818 – Placing a sign from the offhand closes the sign UI immediately.
  • MC-208301/clear does not properly affect the item on the mouse pointer after crafting it.
  • MC-208836 – Villager incorrectly holding spyglass.
  • MC-211666 – Guardians attack invisible axolotls.
  • MC-212127 – Normal ink sac and glow ink sac are not grouped in the creative inventory.
  • MC-212144 – Subtitles refer to Glow Item Frame as "Item Frame".
  • MC-212168Ctrl + Pick Block does not copy block state "lit".
  • MC-212216 – Repeatedly clicking on a sign with an ink sac or glow ink sac abruptly stops the hand animation.
  • MC-212236 – Cannot visually critical-hit a glow squid (No sound/particles).
  • MC-212314 – Glow squid remains dark even if there is a light source block next to it.
  • MC-212325 – Glow Squid entity data (potion effects, custom name, ...) does not get saved.
  • MC-213825 – Using bone meal on a moss block only spreads moss to blocks on the same Y level.
  • MC-214781 – Lava does not generate at the very bottom of noise caves.
  • MC-214784 – Fossils can generate floating in caves.
  • MC-214836 – Water caves cause land to be excessively flooded.
  • MC-214844 – Bedrock can be exposed to the air at the very bottom of the new caves.
  • MC-214970 – Phantoms continously make too much flapping sounds.
  • MC-215194 – Structure blocks do not work below Y=0.
  • MC-215838 – There is currently no way to craft deepslate tiles and deepslate bricks.
  • MC-215847 – Infested stone generates in deepslate areas below mountain biomes.
  • MC-215850 – Deepslate Tile Wall comes before Deepslate Brick Wall but Deepslate Bricks come before Deepslate Tiles in creative inventory.
  • MC-215939 – Emerald ore spawns in lower frequencies than it should above Y=100.
  • MC-216136 – Polished deepslate slab isn't grouped with the other deepslate slabs in creative inventory.
  • MC-216363 – Crash upon replacing soul sand or magma with the other under a tall bubble column using /setblock.
  • MC-216492 – Fox incorrectly holding spyglass.
  • MC-216735 – Stone Lapis Ore generating in Deepslate.
  • MC-216736 – Lava lakes generate exposed in caves.
  • MC-216738 – Deepslate diamond ore texture is shifted a pixel to the right.
  • MC-216765 – Coal ore can generate below Y=0 when attached to a fossil.
  • MC-216817 – Inconsistency: Cobbled deepslate cannot be smelted back into deepslate.
From the previous development version
  • MC-217020 – Gold ore and deepslate gold ore textures are inconsistent.


Video made by slicedlime:


  1. "Minecraft Snapshot 21w10a" – Minecraft.net, March 10, 2021