Slime Tweaker
by eman7blue
Slime Tweaker changes the largest size that naturally spawned slimes can reach, through a gamerule and a config file on NeoForge.
What it does
The gamerule maxSlimeSize sets the maximum size of slimes that spawn naturally. The default cap is 2, and the mod raises it, so larger slimes can appear in a world. Setting the value to 0 turns the effect off, and the spawn chance, depending on the level difficulty, also follows the config. Slimes grow one size larger than normal when spawned under these settings.
Internally, Minecraft stores slime size in three forms: a base size used by the gamerule, an actual size used by the game code, and an NBT size shown in commands. The author explains that the base size is shifted into bits to produce the actual size, which is capped at 127. The gamerule accepts negative numbers as well, and the mod does not change how the slime class itself is copied by related mobs like magma cubes.
The mod is server-side only, so players join a server running it without installing anything. Files are published for NeoForge 1.21.1, and the code is open source under the MIT License.
Key features
Gamerule for natural spawns
The maxSlimeSize gamerule controls how large naturally spawned slimes can become, with a default cap of 2.
Config-based spawn chance
The chance of larger slimes spawning is adjusted through the mod's config and scales with the level difficulty.
Slime size conversion
Base, actual and NBT slime sizes are explained on the page, so server owners can enter the values they need.
Disabling the effect
Setting the gamerule value to 0 turns the larger-slime behavior off without removing the mod.
Gallery
Compatibility
Latest build for each game version and loader.
Only full game releases are shown. This mod publishes no snapshot builds.
Use cases
Solving a specific slime problem
Server owners who find slimes too small or too rare can raise the natural size limit without editing the game code.
Who it’s for: Server owners who want larger natural slimes on NeoForge 1.21.1 servers, and players who want to understand slime sizing in Minecraft.
How it compares
Slime chunk: Spawn-Proof is server-side only and open source under the MIT License, with files for NeoForge 1.21.1, so it covers the same server environment. No Superflat Slimes is a Fabric mod for 1.21.1 – 1.21.11, licensed as All rights reserved, so it does not run on NeoForge. Global Gamerules (Neoforge) is server-side only and open source under the GNU Lesser General Public License v3.0 or later, for NeoForge 1.21.1, and can set gamerules more broadly.
| Mod | Loaders | Game versions | Environment | Updated |
|---|---|---|---|---|
| Slime Tweaker | NeoForge | 1.21 – 1.21.1 | Server-side only | 2024-11-10 |
| Slime chunk: Spawn-Proof | NeoForge | 1.21.1 | Server-side only | 2026-08-18 |
| No Superflat Slimes | Fabric | 1.21.1 – 1.21.11 | Server-side only | 2026-05-14 |
| Global Gamerules (Neoforge) | NeoForge | 1.21.1 | Server-side only | 2026-04-20 |
Questions
Does Slime Tweaker need to be installed on the client?
What does the maxSlimeSize gamerule change?
Which game versions does Slime Tweaker support?
In the catalog
Slime Tweaker is one of 11,058 Mobs mods on ModsFinder, and one of 4,974 Mobs mods for NeoForge. 32,366 mods support Minecraft 1.21.1.
More from eman7blue
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What the author says
Slime Tweaker adds a gamerule to change the size of natural spawning slimes and config to modify more specific values relating to the spawning of slimes. I made this mod to solve an extremely specific problem I was having. Running gamerule maxSlimeSize (number) modifies the max size of slimes than can spawn, capped…
Official listing
- Modrinth page
- modrinth.com/mod/slime-tweaker
- Owner
- eman7blue
- Published
- 2024-11-10
- Updated on Modrinth
- 2024-11-10
- Facts verified
- 2026-10-15