In this paper, we present the Ontology Matching EvaLuation Toolkit (MELT), a software toolkit to facilitate ontology matcher development, configuration, evaluation, and packaging. Compared to existing tools in the ontology matching domain, our framework offers detailed evaluation capabilities on the correspondence level of alignments as well as extensive group evaluation possibilities. A particular focus is put on a streamlined development and evaluation process along with ease of use for matcher developers and evaluators. Our contributions are twofold: We present an open source matching toolkit that integrates well into existing platforms, as well as an exemplary analysis of two OAEI 2018 tracks demonstrating advantages and analytical capabilities of MELT.