QFLib package for Pari/GP. C++ routines for local and global computations with integer-valued quadratic forms. These routines compute local densities (at all places) for integer-valued quadratic forms and check representability of all numbers up to a given (multiplicatively defined) bound. These computations produce the explicit (sharp) lower bound for the constant in the asymptotic expression for the ”representation numbers” r_Q(m) described in the 2004 Duke Math. Journal paper of Hanke ”Local Densities and Explicit Bounds for Representability by a Quadratic Form”.