The increasing adoption of preprinting and of open or transparent peer review are two major developments in the scholarly communication system. To optimally benefit from these developments, it is essential to have high-quality metadata for preprints and open peer reviews, in particular metadata that links preprints to the corresponding journal articles as well as metadata that links peer reviews to the journal articles or preprints to which they pertain.
In this talk, we discuss the increasing adoption of preprinting and open peer review and we explore the availability of metadata for preprints and open peer reviews, in particular metadata made available through Crossref. We present detailed statistics showing the availability of preprint-article links in Crossref, as well as links between peer reviews on the one hand and preprints and journal articles on the other hand. We show examples of good metadata practices, but also shortcomings of the metadata made available through Crossref. We conclude by presenting recommendations for improving metadata practices for preprints and open peer reviews.