Java Edition:Entity Duplication Methods
Specific Entity Duplication Methods
Gravity Block
There have been various methods of duplicating gravity blocks. [1][2] Floating-point precision errors, for example, can allow for duplicating sand, gravel, dragon eggs and anvils at high coordinates prior to 1.4.3.
End Portal Duplication
1.9 - 1.15.1 Having a mob die at the same time it enters a portal will cause the mob to give item drops and be teleported to the other dimension. This method allows for duping items too. [3]
TNT
A TNT block is BUD-powered so that when the contraption is moved by a piston, the TNT is updated and moved at the same time. This results in a primed TNT entity and a block. 1.9 - present [4]
Chunk Savestating
This method allows for duping mobs that are included with structures, i.e. shulkers, elder guardians and even ender dragon.
Horse Duplication
From 13w16b to 13w22a, leaving a server while riding a horse would duplicate the horse upon relogging[5]. This also means that horse armour and saddles can be duplicated. After 12w21a, the player can also duplication donkey's chest inventories which makes this a powerful dupe.
Playerdata Duplication
Tested version range: 12w18a - 1.21 (present).
You can duplicate the playerdata from one player to another by abusing that singleplayer saves player data into two locations: the level.dat file, and into a seperate file located in either the players or playerdata folders. You need at least two accounts for this method.
- Open the world in singleplayer on the account that contains the data you wish to duplicate. Save and exit the world. This will save the data into both level.dat (if it was not already there from singleplayer), and into its own player specific file in the player data folder.
- Open the world in singleplayer again, but with another account. Save and exit the world. Singleplayer will prioritize loading the data in level.dat, and copy that data into its own player specific file in the player data folder. This will overwrite any data pre-existing for that account in the player data folder.
- Now, if the world is opened in a LAN or dedicated server, both accounts will load the copied data from either level.dat or from the player data folder.
Inventories, ender chest contents, potion effects, gamemode, motion, rotation, location, air time, fire time, health, hunger, saturation, experience, and bed location will be copied.