Predictive models for the epidemiology of infection by genetic elements of microbes are necessary to address both their ecological and evolutionary impacts. Metrics have been developed that describe the diversity of the CRISPR spacers and their outcome in simple microbial communities; however, their comparative application to empirical data sets is limited. Rachel Whitaker, Irene Newton and colleagues will develop an accessible genomics tool for analysis of CRISPR population diversity in populations of bacterial genomes.