Minecraft 1.21.1 players can use current Supplementaries releases on Fabric or NeoForge. The safest process is to identify the loader first, then install the matching dependency and mod file.
Choose Fabric or NeoForge
Use the loader already configured for your instance. A NeoForge Supplementaries file is not interchangeable with a Fabric file even when both target Minecraft 1.21.1.
Understand the provided ZIP
The main download on this independent site points to the project’s 1.21.1 source branch archive. That ZIP contains source code and is not the compiled mod JAR normally placed in a player’s mods folder.
Protect your worlds before updating
Back up important worlds before changing mod versions. Update Supplementaries and Moonlight Lib as a compatible pair, then test a copy of the world before committing to a large upgrade.
Related guides
Continue with the focused guides in the sidebar or return to the full Supplementaries Mod guide library.