Lib 39
by 3944Realms
Lib39 is a general-purpose library mod by 3944Realms that other mods can require to add data synchronization, data generation and utility code.
What it does
Lib39 supplies a set of helper classes for mod developers. Its synchronization system moves capability data between server and clients, and it reaches more data types than the default capability sync through a DataProvider. A separate provider generates language JSON files from code, and a compatibility class manages mod registration so that other mods integrate more cleanly.
The library also includes an NBT read and write utility built on a chained pattern, which removes repeated serialization code, and a set of methods for managing riding relationships between entities. Its files show version examples such as 1.20.1-0.0.17, and a built mod contains the library with examples included. The source code is public and carries JavaDoc annotations, so developers can read the classes in a source archive.
Lib39 is published for Fabric, Forge and NeoForge, and it runs on client and server, so both sides need it when a mod that requires it is installed. It is released under the MIT License and is open source. Builds cover 1.20.1 and the 1.21.10 – 1.21.11 versions, with the latest Fabric and Forge file for 1.20.1 and the latest NeoForge file for 1.21.11.
Key features
Capability data synchronization
Synchronizes capability data between server and client, and extends sync to more data types through a DataProvider.
Language JSON generation
Generates I18n language JSON files from code, so translations can be produced by data generation.
NBT read and write utility
Chained helper methods for reading and writing NBT data, removing repeated serialization logic.
Riding relationship methods
Methods for creating, reading and managing which entities ride which, without custom bookkeeping.
Compatibility
Latest build for each game version and loader.
Only full game releases are shown. This mod publishes no snapshot builds.
How it compares
Brick Lib API is open source under the Apache License 2.0 and covers Fabric, Forge and NeoForge for 1.18.2 – 1.21.5. NexusLib is a client and server library for Fabric and NeoForge 1.21 – 1.21.1 under a custom license and is not open source. WrapperLib is open source under the Mozilla Public License 2.0, for Fabric, Forge and Quilt across 1.16.5 – 1.19.3.
| Mod | Loaders | Game versions | Environment | Updated |
|---|---|---|---|---|
| Lib 39 | Fabric, Forge and NeoForge | 1.20.1 – 1.21.11 | Client and server | 2026-04-19 |
| Brick Lib API | Fabric, Forge and NeoForge | 1.18.2 – 1.21.5 | Not published | 2026-03-22 |
| NexusLib | Fabric and NeoForge | 1.21 – 1.21.1 | Client and server | 2026-09-18 |
| WrapperLib | Fabric, Forge and Quilt | 1.16.5 – 1.19.3 | Client and server | 2023-01-24 |
Questions
Which loaders does the library support?
Does the library need to be installed on the server?
Where can the source code be found?
In the catalog
Lib 39 is one of 3,514 Library mods on ModsFinder, and one of 2,348 Library mods for Fabric. 19,862 mods support Minecraft 1.21.11.
More from 3944Realms
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What the author says
After building, this mod can be found in the library with examples included. Click "Download Source Code" in the right-hand window to view JavaDoc annotations.
Official listing
- Modrinth page
- modrinth.com/mod/lib-39
- Owner
- 3944Realms
- Published
- 2025-10-25
- Updated on Modrinth
- 2026-04-19
- Facts verified
- 2026-10-15