Lib39
by exaptations
Lib39 is a library of utility classes, mixins and events, collected from the Yttr content mod and packaged for Fabric and Quilt.
What it does
Lib39 gathers loose utilities, mixins and events that originated in the Yttr mod. The author notes that many of these pieces were pulled out of Yttr because they proved useful on their own, and the project is meant to be split into small modules rather than one large library.
Each module is small. The author distributes them through Modrinth and encourages jar-in-jar packaging, so a mod that uses only part of the library can carry just the modules it needs. Server owners and developers can replace the core with the modules they choose.
Lib39 is published for 1.18.2 – 1.20.1 across five release versions. Support for 1.20.1 comes from experimental builds in the earlier line, and version 2.0 is API-compatible with the 1.x line and is currently available only for 1.20.1, developed alongside Lucium, which requires it.
Key features
Mixins and events
The library provides mixin helpers and event hooks that other mods can call without bundling their own copies.
Modular packaging
Functionality is split into small jar-in-jar modules, so each module can be included or left out by the mod that uses it.
Utility classes
A loose collection of general-purpose helpers, drawn from the code the Yttr project was built on.
Swappable core
The core can be replaced with whichever modules a developer wants, instead of depending on a single fixed package.
Compatibility
Latest build for each game version and loader.
Only full game releases are shown. This mod publishes no snapshot builds.
Required by 1 mod
Use cases
Developers bundling a single helper
A mod author can jar-in-jar only the Lib39 module it needs, keeping the final file small.
Lucium users
Players running Lucium need Lib39 2.0, which is the release built for 1.20.1.
Who it’s for: Mod developers who want shared utilities and mixin helpers without a large dependency, and players of mods that list Lib39 as a requirement.
Questions
Which loaders does Lib39 support?
Does Lib39 have to be installed on both sides?
Which mod requires Lib39?
Why are Lib39 modules packaged separately?
In the catalog
Lib39 is one of 3,514 Library mods on ModsFinder, and one of 2,348 Library mods for Fabric. 34,764 mods support Minecraft 1.20.1.
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What the author says
Lib39 is a loose collection of utilities, mixins, events, etc originating in our content mod Yttr — people constantly talk about "stealing" mixins from Yttr since it has so many random useful things in it, so we decided it'd be a good thing to split it up into a library. Lib39 is also distributed on Modrinth, but you…
Official listing
- Modrinth page
- modrinth.com/mod/lib39
- Owner
- exaptations
- Published
- 2022-08-16
- Updated on Modrinth
- 2026-08-09
- Facts verified
- 2026-10-15