Inventory System is a complete item toolkit for Godot 4. Items are ItemDefinition resources (rarity, category, stack size, equipment slot, stat modifiers, value, weight, use effects, generated tooltips) found by an ItemDatabase that scans a folder of .tres files. An Inventory resource handles stacking, split, merge, swap, sort, capacity, filters and an optional weight limit; Equipment aggregates stats; hotbars, recipes with tools and stations, seeded loot tables and shops with stock limits are included.

Every change is a command that returns a result code and is also a serialisable dictionary (apply_op), so a local game, a host or a server can validate and replay the same request; an InventoryAuthority and an ENet example show server-authoritative inventories. The UI offers grid and list views, drag and drop, split, context menu, keyboard and gamepad pick-and-place, comparison tooltips, equipment, hotbar, crafting with can-craft highlighting, chest and shop windows, all themeable, with no globals so split-screen co-op works. Saves are versioned JSON.

The add-on lives in addons/mammoth_inventory/ so it can be copied into any project; the demo has three item sets (fantasy, sci-fi survival, cozy farm) with 74 generated icons. All code, art and sound are original and CC0.