Add to ORKGWe present Build Analyzer, a tool that helps developers optimize the build performance of huge systems written in C Due to complex C header dependencies, even small code changes can cause extremely long rebuilds, which are problematic when code is shared and modified by teams of hundreds of individuals. Build Analyzer supports several use cases. For developers, it provides an estimate of the build impact and distribution caused by a given change. For architects, it shows why a build is costly, how its cost is spread over the entire code base, which headers cause build bottlenecks, and suggests ways to refactor these to reduce the cost. We demonstrate Build Analyzer with a use-case on a real industry code base.</p