XFdtd is electromagnetic simulation software with a very wide variety of applications in RF circuit, antenna, military/defense, medical EM, photonics, radar, component, metamaterial, and related fields. It originally stood for X (Window System) Finite Difference Time Domain and was first developed in the mid 1990s by Remcom Incorporated[1] of State College, PA in the United States. XFdtd includes full wave (FDTD), electrostatic, thermal-biological, circuit, and 2D Eigen solver and integrates with PO/MEC, and GTD/UTD method solvers.