Java Edition 1.21.5 Pre-Release 1

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1.21.5 Pre-Release 1 (known as 1.21.5-pre1 in the launcher) is the first pre-release for Java Edition 1.21.5, released on March 11, 2025.^[1] This is the first pre-release released in 2025.

Spawn eggs

• Added textures for Programmer Art resource pack.

Fallen trees

• The longer versions of fallen birch trees now generate properly.
  • This version is up to 15 blocks long, as opposed to the shorter version which can only reach 8 blocks at most.

General

• Arguments in commands that accept inline values like loot tables, predicates, modifiers, data components, formatted text (/loot, /give, /tellraw, /execute if predicate, data components in /execute if items, etc.) have been reverted to accept numbers in place of booleans.

Network protocol

• The client-bound player_chat packet now contains an index increasing for every message sent to the client.
  • The index starts at 0 when logging in (or is reset by configuration phase and the login packet).
  • For every message, the server should increment this value by 1.
  • If this value updates in an unexpected way, the client will disconnect.
  • As the protocol requires that every chat packet reaches the client in produced order, the goal is to enable faster detection of missed/reordered chat messages for custom server developers.
• The server-bound chat and chat_command_signed packets now contain a checksum byte along with the 'last seen' update.
  • This is a simple hash of the 'last seen' signatures which should be reconstructed by the server, allowing quicker detection of desynchronized state.
  • This can be passed as 0 to disable the check, for compatibility with protocol translation.

Resource pack

• The version is now 55.
• Tweaked leaf litter block models.

15 issues fixed

From released versions before 1.21

• MC-170134 – Minecraft uses several times more VRAM than needed after exploring terrain for a while.

From the 1.21.5 development versions

• MC-279350 – Leaf litter multipart model system is unoptimized, causing render lag.
• MC-280141 – Baby farm animals from spawn eggs with a variant differing from the parent flash the wrong variant initially.
• MC-280241 – Cold Cows have improperly mirrored and incorrectly aligned ear textures.
• MC-280249 – Spawn eggs don't use their old textures with the Programmer Art resource pack enabled.
• MC-280278 – Sheep wool uses 1.14 texture with Programmer Art resource pack enabled.
• MC-280326 – When teleporting across dimensions an error is often thrown.
• MC-280361 – When a fallen tree replaces the bottom half of tall vegetation, the top part of the vegetation still generates.

From the previous development version

• MC-280474 – TNT minecarts explode regardless of tntExplodes gamerule.
• MC-280477 – TNT still explodes when summoned or dispensed while tntExplodes gamerule is false.
• MC-280479 – TNT is completely deleted when attempting to ignite it using redstone pulses when the "tntExplodes" gamerule is disabled.
• MC-280480 – No flint and steel clicking sound when attempting to ignite. TNT with a flint and steel when the "tntExplodes" gamerule is disabled.
• MC-280493 – If the tntExplodes game rule is changed to false while primed TNT already exists in the world, the primed TNT explodes as normal.
• MC-280501 – The "Fire extinguishes" sound plays every game tick while on fire in rain.
• MC-280520 – ItemDropChance on an item frame is not serialized when there is no item anymore, leading to inconsistencies.