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:!: This page is irrelevant, most mods are now on Loader 0.4.x, and should be removed from the sidebar and kept archived for miscellaneous use.

Loader 0.4.x and You!

This tutorial lists what you need to know to update your mods to Loader 0.4.x (and beyond!?).

Schema changes

The schema has changed somewhat. Throughout 0.4.x, the schemaVersion 0 will be supported, but no such promises are made for 0.5.x and beyond.

Useful sources:

Nested JARs

There has been a lot of confusion about what nested JARs are meant to be used for.

Nested JARs are:

  • a solution to provide dependencies which are in the form of Fabric mods, allowing the loader to pick the best version matching a given modpack's sets of dependencies,
  • a solution that allows you turning libraries into Fabric mods and avoiding conflicts where they are not cleanly shadowable or where there is good reason for a Fabric mod developer to be the authoritative versioning source,
  • a potential solution to cleanly package subprojects/submodules of a mod in one “combined” JAR, while also allowing using them separately.

Nested JARs are not:

  • meant to be used on non-mod Java libraries,
  • always the best solution for libraries which can be safely shadowed under a different package. Keep in mind that a Fabric mod ID can only exist once, meaning that potential version conflicts could prevent a pack from loading - shadowed libraries do not have this problem.

In doubt, refer to this helpful chart:


  • If your mod is using plugin-loader, please abandon it and adopt the entrypoints system instead.
tutorial/loader04x.txt · Last modified: 2023/12/27 12:58 by