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Minecraft Wiki
Minecraft 12w39b
SP 12w39a image.png
Java Edition 12w39b.png

Java Edition



Release date

September 28, 2012

Snapshot for



Client (.json)
Server (.exe)

Protocol version


12w39b is the ninth snapshot for Java Edition 1.4.2, and was released to fix some of the bugs and crashes in the 12w39a snapshot.[1]



Mob spawners
  • More options to customize spawners.
  • Can now have their range and maximum spawn limit customized.


Custom potions
  • Only available by editing in with a world editor.
  • Able to create potions with multiple effects.

Command format[]

  • Added a command variable to the command.
    • Use "L" after number to represent number of levels, not number of xp.
    • For example "/xp 4L" will give a player 4 levels.
Target selectors
  • Added command block arguments.
    • Added "l" and "lm" arguments for indicating players with a maximum level, and minimum level, respectively.
    • Added "r" and "lr" arguments for indicating the maximum and minimum range to which players will be affected.


7 bugs fixed

  • Fixed block placement issues with lighting.[2]
  • Game performance is now better from before.
  • Fixed Bottomless pit.
  • Pumpkin emitting stronger light from the wrong face fixed.
  • Fixed the witch's texture being weird.
  • Partially fixed Nether lag by making the server do some of what used to be the client's work and increasing chunk load time slightly.[3]
  • Fixed some lighting bugs related to upside down slabs and stairs and farmland.