AntiNbtKick
AntiNbtKick is a Fabric optimization mod that stops players from picking up items once their inventory data would exceed the NBT size limit that gets a client kicked.
What it does
A player whose inventory data grows past the server limit can be disconnected, and the mod works to prevent that. It calculates the byte size of items with the same CODEC-based encoding Minecraft uses, adds 128 bytes of overhead for each slot, and enforces a total cap of 1,777,777 bytes across the main inventory, hotbar, offhand and armor slots.
Each action that would push the inventory over the cap is refused: picking up items from the ground, placing items, dragging stacks, and moving items into containers in survival and creative mode, including creative cloning and painting. Blocked items are dropped silently, and moving items between containers and the inventory is still allowed even when the total is over the limit. The mod is client-side only, so players install it and servers do not need it.
Key features
Accurate size checks
Item sizes are computed from Minecraft's own CODEC encoding rather than estimated, so the total tracks the real data.
Ground pickup blocking
Items that would take the inventory past the limit are refused on the ground and quietly left where they are.
Container and drag control
Single clicks, drag operations and container deposits are checked, and moves that exceed the limit are stopped.
Creative mode protection
Creative placement, dragging, painting and middle-click cloning of oversized items are all blocked.
Compatibility
Latest build for each game version and loader.
1.21.x12 of 12 versions with builds
1.20.x2 of 2 versions with builds
Only full game releases are shown. This mod publishes no snapshot builds.
Use cases
Survival servers with large stacks
Server owners whose players carry heavily enchanted or data-rich items can keep those players from being kicked for oversized NBT data.
Who it’s for: Players on Fabric servers that have hit the NBT size limit, and players who want to avoid disconnects caused by large inventories.
How it compares
NBTSize is client-side only, open source under the GNU Lesser General Public License v3.0 only, and published for 1.21.11 – 26.3, so it covers a different version range. Full Inventory GUI is client and server, not open source, under All rights reserved, and built for 1.20.1 – 1.21.11. Maikura Inventory Expansion is client and server, open source under the MIT License, and published only for 1.21.11.
| Mod | Loaders | Game versions | Environment | Updated |
|---|---|---|---|---|
| AntiNbtKick | Fabric | 1.20.5 – 1.21.11 | Client-side only | 2026-06-11 |
| NBTSize | Fabric | 1.21.11 – 26.3 | Client-side only | 2026-09-26 |
| Full Inventory GUI | Fabric | 1.20.1 – 1.21.11 | Client and server | 2026-02-28 |
| Maikura Inventory Expansion | Fabric | 1.21.11 | Client and server | 2026-06-20 |
Questions
Does AntiNbtKick need to be installed on the server?
Which Minecraft versions does AntiNbtKick support?
In the catalog
AntiNbtKick is one of 3,545 Optimization mods on ModsFinder, and one of 2,575 Optimization mods for Fabric. 19,862 mods support Minecraft 1.21.11.
More from UnicornMaster
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What the author says
A Fabric mod that prevents players from getting kicked due to oversized NBT data in their inventory. This mod intelligently monitors and restricts inventory size to keep you safe from server kicks while still allowing you to manage your items effectively. Ground Item Pickup: - Prevents picking up items that would…
Official listing
- Modrinth page
- modrinth.com/mod/antinbtkick
- Owner
- UnicornMaster
- Published
- 2026-03-18
- Updated on Modrinth
- 2026-06-11
- Facts verified
- 2026-10-15