The Unimodularity Library is a software library written in C++ that implements an efficient algorithm for testing total unimodularity, based on Seymour’s decomposition theorem [1] for regular matroids. The algorithm runs in O( (n+m)^5 ) time and is a simplified version of the cubic algorithm of [2]. The algorithm can also test for the related properties of unimodularity and strong unimodularity.