Cobaltmetrics crawls the web to index hyperlinks and persistent identifiers as first-class citations. We analyze a wide range of websites to reveal insightful links between documents. Cobaltmetrics goes deeper than backlink databases and altmetrics aggregators to help you report on all types of content: publications, books, clinical trials, patents, software artifacts, derivative works, etc. The web is our corpus, and our URI transmutation API collates citations to all known versions of a document. See https://cobaltmetrics.com/ for more information.