Directory

Membership organization that registers DOIs for scholarly content and exposes the metadata through a free public REST API, content negotiation and the paid Metadata Plus service

Non-profit registry of persistent researcher identifiers (ORCID iDs) with user-controlled records, Public and Member APIs, OAuth sign-in and an annual CC0 public data file

Elsevier-owned preprint and working-paper platform with discipline networks, author pages, download rankings and institutional research paper series, free to post and read