Ukulib Mod Common Errors and a Better Troubleshooting Order

Most Ukulib problems are dependency-chain problems. The fastest fix is usually to identify the first mismatch in the log instead of reinstalling the entire profile.

Error: Ukulib is missing

Verify that the Ukulib JAR is in the mods folder for the exact launcher instance being started. Then check whether the installed build matches the profile’s loader.

Error: required version is not satisfied

Compare the dependent mod’s declared Ukulib range with the installed version. A newer library can still be incompatible if the dependent mod has not been updated for its API changes.

Error: Fabric and NeoForge files are mixed

Current 2.x releases are loader-specific. A file intended for one loader should not be treated as a universal JAR for the other.

Error: duplicate libraries or classes

Remove outdated duplicate Ukulib copies from the same instance unless the setup explicitly requires otherwise. Duplicate versions can confuse dependency resolution or class loading.

Issue around ModMenu title-screen integration

The 2.1.1 release specifically fixed compatibility with ModMenu’s title-screen button and corrected player-head visibility when the Ukulib button was disabled. If your symptoms match those notes, confirm which Ukulib release you are running.

A repeatable debug method

Back up the profile, reduce it to the required mod set, launch once, record the first relevant log error, change one dependency, and repeat. This produces better evidence than changing many files between launches.

Continue with the site guides

Use the compatibility section to check versions, then review the troubleshooting section before changing several dependencies at once.