Sometimes third party libs add code in the PreProcessBuild step. Or they do not implement the External Dependency Manager properly (Advertisement SDKs, I am looking at you). How does it work? To resolve the resulting "duplicate class" errors quickly I've built this tool. It shows which libraries are in conflict and where they are coming from (including gradle files). It's not a pre build tool but a POST build tool. Meaning it will catch errors that the External Dependency Manager is not aware of. Asset Store Link https://assetstore.unity.com/packages/slug/222357 1) Analyze the errors after the build and gain insights: 2) List duplicate libraries before the build. 3) Find all libraries in the project.