CSL provides an easy-to-use but feature-rich XML language to describe bibliographic and citation formatting. It has been developed alongside CiteProc. Analogous to BibTeX .bst files or the binary equivalents in proprietary applications like Endnote, CSL is open, international-ready, and designed on a solid foundation that yields a language that is easy-to-use, while able to flexibly-but-reliably format bibliographies and citations for a wide variety of fields.