Shadow Items Mod

A shadow item is one stack that appears in two places at the same time, for example in two different players' inventories. Moving or changing one copy updates the other immediately, so the stack is not duplicated. Players can link items with a vortex labeled Linked, which creates the paired copies, and remove a link by taking half a stack from a slot, dropping an item from a dispenser, or placing an item in a hopper labeled UnLinked.

The mod keeps an internal registry of every linked slot. It scans player inventories and entity inventories, including entity blocks such as chests on minecarts, but it does not scan dropped entity items. Each shadow item is tied to an internal ID, which lets the registry find and synchronize the copies. Links survive a server restart and a simple chunk unload, and a linked stack is restored when it returns. Nested containers are the one weak point: a shulker box holding a shadow item loses its link once it is placed on the ground.

Shadow Items Mod is server-side only, so players join without installing anything. It is published for Fabric alone, with files for 1.21 – 1.21.8 and 1.0.1 for 1.21.8 as the latest file. The code is not open source; the mod is released under All rights reserved. The author links a source repository and an issue tracker for bug reports.