Abstract Introduced in this paper is a software package called SPHERE, meant for the optimization of spherical four-bar linkages for problems of path generation and rigid-body guidance. The optimization methodology is based on an equality-constrained least-squares scheme, as described elsewhere. Considering the similarities of the two problems, we established a more general formulation to cover both synthesis cases. SPHERE is developed based on this formulation. An outline of the methodology and the package is presented in this paper. Two examples are included to illustrate the usage of the package.