Single-molecule localization microscopy (SMLM) is a family of super-resolution microscopy techniques based on localizing clusters of detected photons that are emitted by single molecules. The localization procedure is based on careful statistical analysis of long image sequences to derive the nanometer positions of the molecules. By introducing additional optics, such as cylindrical lenses in the optical system, SMLM techniques have been extended to 3D super-resolution imaging. This adds a calibration step, thereby further complicating the data analysis. Here we present Huygens Localizer, a well-supported user-friendly package that carries out these tasks quickly by offloading carefully designed 2D and 3D analysis and visualization procedures to massively parallel graphical processors (GPUs).