CodeQL is a powerful and versatile static analysis tool, and at Trail of Bits, we regularly use CodeQL on client engagements to find common vulnerabilities and to perform variant analysis for already identified weaknesses. In this latest addition to the Testing Handbook, we describe how to set up CodeQL locally and create a CodeQL database for your project. Whether you’re an experienced CodeQL user or just getting started, our Testing Handbook is your entry point for harnessing the full power of CodeQL.