In this white paper, we will introduce “Tidy3D”, Flexcompute’s simulation tool for electromagnetic modeling. Implementing one of the most general and widely used algorithms for electromagnetics(FDTD), it is applicable to an extremely wide range of systems and devices. The software is designed for maximum user-friendliness by combining the flexibility and simplicity of a scripting-based interface with the performance of advanced computing hardware in the cloud. All aspects of the implementation, from the underlying algorithm to the adaptive allocation of compute resources, are tailored and optimized for the highest performance on Flexcompute’s hardware. The resulting product finds solutions 100x faster and can handle 100x larger problems than conventional CPU-based solvers. Through Tidy3D, engineers and researchers can iterate through designs orders of magnitude faster and model problems previously out of reach, resulting in a dramatic acceleration to research and product development.