DSJM: A Software Toolkit for Direct Determination of Sparse Jacobian Matrices. We describe the architecture and implementation of DSJM, a software toolkit written in portable C++ that enables direct determination of sparse Jacobian matrices. Our design exploits the recently proposed unifying framework ”pattern graph” and employs cache-friendly array-based sparse data structures. The pattern graph remains invariant for one-sided, two-sided, full column, and column-segments compression algorithms.The DSJM implements a greedy partitioning algorithm after the sparse matrix has been preprocessed with ordering heuristics for efficiency. In our numerical testing on 20 large-scale test instances (see Graph Models and their efficient implementation for sparse Jacobian matrix determination, Disc. Appl. Math. 161(2013) 1747-1754) we have found that DSJM consistently produced better timing and partitions compared with similar software.