Leukocyte
by NucleoidMC
Leukocyte is a server-side protection tool that limits building, breaking and interaction inside named regions of a world, set by commands.
What it does
Protection in Leukocyte is organized around authorities, which are named rule sets applied to players within a region. Each authority gets a unique name and a priority level, and it can list player exclusions. A rule such as break, place, block drops, interact blocks or interact entities can be set to allow or deny, so a server can stop block placement inside a single authority by naming it and denying that rule. An authority is removed later with the protect remove command.
Regions are built as shapes. A shape starts with a protect shape start command, and primitives are then added with commands: the universe, a whole dimension, or a cuboid between two block coordinates. The commands can run several times to compose a larger shape, and once it is finished it is saved under a given name and tied to an authority. A shape can be removed later with protect shape remove. Leukocyte needs Fabric API on Fabric and Quilt, and it is open source under the GNU Lesser General Public License v3.0 only. The mod is server-side only, so players join without installing it.
Key features
Named authorities
Each authority holds a set of protection rules, a priority level and optional player exclusions, and it can be removed by name.
Per-action rules
Rules control breaking and placing blocks, block drops, and interaction with blocks and entities, each set to allow or deny.
Composed shapes
Regions are built from a universe, a dimension or cuboids between two coordinates, combined by commands into one shape.
Priority levels
Higher levels win over lower ones, so an authority at level 10 overrides an overlapping authority at level -1.
Compatibility
Latest build for each game version and loader.
26.x3 of 3 versions with builds
1.21.x8 of 8 versions with builds
1.20.x5 of 5 versions with builds
1.19.x4 of 4 versions with builds
1.18.x2 of 2 versions with builds
This mod also publishes snapshot builds. Snapshots are not shown in the matrix.
Requirements
Dependencies declared by the latest file for each loader.
Required 1
Use cases
Spawn protection
A server can set an authority over a spawn area that denies block placement and breaking for all players except listed exclusions.
Minigame arenas
Event maps can use shapes to mark arena cuboids and set rules that only apply inside them while the rest of the world stays open.
Who it’s for: Server owners and map makers who want to limit building or interaction inside specific parts of a world with commands rather than plugins or data packs.
Questions
Does Leukocyte need to be installed on players' clients?
Which loaders does Leukocyte support?
How are protected regions saved?
In the catalog
Leukocyte is one of 8,016 Management mods on ModsFinder, and one of 5,930 Management mods for Fabric. 8,071 mods support Minecraft 26.3.
More from NucleoidMC
Similar mods
What the author says
The basis of world protection with leukocyte is an "authority". An authority is responsible for applying specific rules to players within it. An authority has a unique name, as well as a priority ("level"), and set of player exclusions. An authority can be later removed with /protect remove.
Official listing
- Modrinth page
- modrinth.com/mod/leukocyte
- Owner
- NucleoidMC
- Published
- 2021-12-17
- Updated on Modrinth
- 2026-10-10
- Facts verified
- 2026-10-15