ChaosTools.jl is a Julia library providing tools for analyzing nonlinear dynamics and chaotic behavior. It offers functionality for calculating Lyapunov exponents, detecting chaos via methods like GALI and the 0-1 test, analyzing predictability, finding fixed points and periodic orbits, estimating signal periods, analyzing rare events through return time statistics, and performing dimensionality reduction. The package is designed to work with DynamicalSystems.jl and can be used as a standalone package or as part of the broader DynamicalSystems ecosystem. The architecture follows a modular organization with functions grouped by topic (chaos detection, dimensionality reduction, periodicity, etc.), leveraging Julia's multiple dispatch and type system for clean, reusable code.