Minecraft wiki entry for Block_and_item_duplication, associated text: This duplication glitch works on Singleplayer and Multiplayer. All you have to do is place a chest in front of you and then leave the server as it saves your player data, then relog and put the items you want to dupe from your inventory in the chest, get a book and quill, overload the book with excessive characters and it will cause you to get kicked from the server and rolling back your player data to last save while server files stay the same. As a result, the items will be in both your inventory and the chest. (requires fabric download and custom download to work) Video here: https://youtu.be/ml3HkqNfUH4