ModsFinder

Long NBT Killer

by TachibanaSherry

Long NBT Killer stops Minecraft from crashing when it meets deeply nested NBT tags, a server-side fix for saved data.

FabricForgeNeoForgeServer-side onlyCustom license1.20.1 – 1.21.8

What it does

A compound or list NBT tag nested deeper than 512 levels is treated as abnormal during a save check. Instead of crashing, the mod writes a warning to the log and lets the game continue, so the deep structure can be inspected later with an NBT editor. Only the server needs the mod, so players join without installing anything. It is published for Fabric, Forge and NeoForge, with files for 1.20.1, 1.20.2, 1.21.1, 1.21.2, 1.21.3 and 1.21.8, under a custom license that is not open source.

Key features

  1. Crash prevention

    Deeply nested NBT tags no longer bring the game down during a save, because the mod intercepts the error.

  2. Depth limit of 512

    Compound and list tags nested beyond 512 levels are flagged as abnormal and logged for later inspection.

  3. Log warning instead of a crash

    The mod replaces the crash with a harmless log entry, letting the server keep running.

Compatibility

Latest build for each game version and loader.

1.21.8Fabric-1.21.8-1.0.0Not availableNeoForge-1.21.8-1.0.0
1.21.3Not availableForge-1.21.3-1.0.0NeoForge-1.21.3-1.0.0
1.21.2Not availableForge-1.21.3-1.0.0NeoForge-1.21.3-1.0.0
1.21.1Not availableForge-1.21.3-1.0.0NeoForge-1.21.3-1.0.0
1.20.2Not availableForge-1.20.2-1.0.0Not available
1.20.1Not availableForge-1.20.2-1.0.0Not available
ReleaseBetaAlphaNot available

Only full game releases are shown. This mod publishes no snapshot builds.

How it compares

Full comparison

Bundle Crash Fix is server-side only, has a custom license that is not open source, and covers 1.21.2 – 1.21.4 on Fabric, Forge, NeoForge and Quilt. Better Combat NBT fix is open source under the MIT License, runs on client and server, and covers 1.18 – 1.20.1 on Fabric and Forge.

ModLoadersGame versionsEnvironmentUpdated
Long NBT KillerFabric, Forge and NeoForge1.20.1 – 1.21.8Server-side only2026-02-03
Bundle Crash FixFabric, Forge, NeoForge and Quilt1.21.2 – 1.21.4Server-side only2025-05-04
Better Combat NBT fixFabric and Forge1.18 – 1.20.1Client and server2025-05-28

Questions

Does Long NBT Killer need to be on the client?

No. Server owners install it, and players connect with no copy of their own.

In the catalog

Long NBT Killer is one of 3,545 Optimization mods on ModsFinder, and one of 2,575 Optimization mods for Fabric. 17,695 mods support Minecraft 1.21.8.

Optimization mods3,545Fabric modsMods for 1.21.817,695

More from TachibanaSherry

All projects
NonConflictKeys1.12.2 – 1.19.40Pack2Reload1.20.1 – 1.21.1Modern KeyBinding1.7.10 – 1.20.4PatPatPat1.6.4 – 1.20.2Quit1.7.10 – 1.20.2VeryLegacyZoomer1.6.4 – 1.7.10

Similar mods

Sodium1.16.3 – 26.3Iris Shaders1.16.5 – 26.3Entity Cullingb1.7.3 – 26.3FerriteCore1.16.5 – 26.3ImmediatelyFast1.18.2 – 26.3Sodium Extra1.16.2 – 26.3

What the author says

This mod replaced the annoying mechanism with a harmless log warning, and let the game go ahead.
TachibanaSherry, on the Modrinth page

Official listing

Owner
TachibanaSherry
Published
2026-02-03
Updated on Modrinth
2026-02-03
Facts verified
2026-10-15

Tags

Optimization
Open on ModrinthCompare