Modded Server Missing Mod Dependency

Direct answer

Read the loader’s dependency report and install the exact required mod/library and compatible version range for this pack. “Newest available” is not automatically correct; keep the server and client on the intended pack release.

What it means

Many mods require libraries or other mods; loaders normally report the missing dependency and required version during startup.

If you are a player

• Use the exact modpack profile the server expects: Minecraft version, loader, pack release, and required client-side mods.
• Do not “update everything” one mod at a time unless the pack author documents that combination; it can create a different mismatch.
• Save your client latest.log or crash report from the failed attempt and give the owner the first loader/registry/Mixin error.

If you run the server

1. Use the loader’s first dependency/sidedness error to identify the exact mod and required version range/environment.
2. Match the intended Minecraft version, loader version, and modpack manifest rather than simply installing the newest release of each component.
3. Keep true client-only mods off dedicated servers and ensure required server/common dependencies are present.
4. Change one mod/dependency at a time on a test copy and keep the original pack/world backup for rollback.

References

Use the documentation for the exact software and release you run. These sources support the settings or diagnostic behavior used in this fix.

Focused diagnostic check: Copy the loader's complete missing-mod and version-range message, not only the final crash line. Match the exact Minecraft version, loader family and library mod release. Fabric, Forge and NeoForge artifacts are not interchangeable; clients may also require the same gameplay mod set.

• PaperMC: Basic troubleshooting
• NeoForged Docs: Sides
• NeoForged Docs: Mod dependency configuration
• Forge Docs: Mod Files and dependency version ranges

Related fixes and guides