Moonlight Lib is the required dependency for Supplementaries. A dependency is shared code another mod expects to find at launch, so version and loader compatibility matter just as much as installing the main mod itself.
Why Moonlight Lib is required
Supplementaries relies on functionality provided by Moonlight Lib. If the loader cannot find a compatible Moonlight build, it can stop the game before a world opens.
Match three labels
Compare Minecraft version, loader and dependency version together. A Fabric Moonlight file does not satisfy a NeoForge environment, and a different Minecraft target may not satisfy the requested version range.
Troubleshooting dependency messages
Read the first clear dependency line in the loader error. Remove duplicate or wrong-loader libraries, then install one compatible Moonlight build and retry with a minimal mod set.
Related guides
Continue with the focused guides in the sidebar or return to the full Supplementaries Mod guide library.