When building fat jar with log4j2, all meta-inf subdirs (org/apache/logging/...,services, ), manifest.mf (possibly merged, if other classes also need entries) from lag4j2-core jar need to be included as a minimum in fat jar. I also included log4j-*.dtd and .xsd files from log4j2-core. Solved for me and tested on log4j2 version 2.23.1.