What Services Does Crossref Offer?

Crossref provides a suite of services built around one core function: registering and sharing scholarly metadata. Its main offerings include Content Registration (DOI registration and metadata deposit), Metadata Retrieval and Metadata Plus, reference linking support, Similarity Check, Cited-by, Crossmark, the Research Organization Registry (ROR), the Open Funder Registry (OFR), and the Grant Linking System (GLS). These services are aimed at member organizations such as publishers, societies, and research institutions, as well as the broader community of tools and services that consume Crossref metadata through its APIs.

Content Registration: The Foundation

Content Registration is the service through which members register records and assign DOIs to scholarly outputs. According to Crossref, members register around 37,000 records daily, and all of this metadata is openly shared with the global scholarly community through free APIs. This is the entry point for most members: you join, then register and maintain your records following Crossref's metadata principles and practices and its schema library.

Metadata Retrieval and Metadata Plus

Metadata Retrieval covers the APIs and services used to access registered metadata. Crossref reports over two billion API calls per month, signalling use by hundreds of tools and services worldwide. Metadata Plus is a separate service listed alongside Metadata Retrieval for organizations that need enhanced access to metadata. Documentation for both sits under the Documentation section of the site.

Services That Build on Registered Metadata

Several Crossref services extend what registered metadata can do:

• Support for Reference Linking — helps link citations between publications.
• Similarity Check — a service for checking similarity of submitted content.
• Cited-by — surfaces citation relationships between works.
• Crossmark — a multi-publisher initiative providing a standard way to access current document status, including updates and corrections.

Registries and Identifier Services

Crossref also offers or supports several registries and linking systems:

How the Pieces Fit Together

The practical picture is a pipeline: members register content and deposit metadata; that metadata is then openly available through APIs; and services like reference linking, Similarity Check, Cited-by, and Crossmark operate on top of that shared metadata layer. External tools consume the same metadata — for example, Crossref's blog describes how Grobid, an open-source tool maintained by Luca Foppiano, uses Crossref metadata to improve extraction and enrichment of bibliographic information from scholarly PDFs. That example illustrates the broader point: the value of registration extends beyond the DOI itself to the tooling and discovery services built on the metadata.

Getting Started

Crossref's site organizes access into four paths: Get involved (become a member, events, service providers, special programs, working groups, code of conduct, fees), Find a service (the service overview and individual service pages), Documentation (setting up as a member, metadata principles and practices, schema library, reports, and service-specific docs), and About us (operations and sustainability, governance, publications, strategic agenda, people, jobs). Prospective members should start with the membership and fees information; existing members and integrators should start with Documentation. Note that membership and fees details are covered on Crossref's own pages — check those directly for current terms rather than assuming any service is free or requires no account.