Documentation

Metadata Retrieval

Crossref metadata is freely available for the community.

We provide open, comprehensive metadata on scholarly works. By collecting metadata from a wide number of organisations, we significantly simplify the downstream use and analysis of scholarly research outputs. For each content item, we collect rich metadata that can be put to a variety of uses.

The metadata can be freely accessed through:

• User interfaces for people to access metadata in human-readable formats.
• APIs for computers to access metadata in structured formats.
• Bulk downloads to get all metadata.
• Member services to check deposited content.

This page provides a general overview, with a brief summary of services. Use the navigation on the left to access full documentation for each service and examples to get started. You can also visit our learning hub. If you have any questions, suggestions or feedback, join the conversation at our community forum.

On this page

• Access and authentication
• Sources of metadata
• Licensing
• Summary of services

Access and authentication

We make our metadata open and accessible. You don’t need to register to use any of our interfaces.

All of our APIs provide public options and almost all requests can be made anonymously. We recommend that you identify yourself by providing an email address. This helps us in the unlikely event that your use of the API causes a problem. We don’t use this information for marketing or any other purpose and logs are deleted after three months. Note that if you use our metadata anonymously, your IP address and the content of your request is still logged.

Our APIs offer various options identification and authentication. Not all are available for all APIs, refer to the documentation for each API for details.

Sources of metadata

Our metadata contains information about scholarly outputs, their properties, and relationships. We rely primarily on deposits by members and don’t scrape websites or full text documents. Our metadata comes from the following sources:

Metadata from members

We are a DOI registration agency with over 20,000 members. We collect metadata with each registered DOI, including information about where it was published and how it should be cited. Members also tell us about relationships to other research outputs, people, and organisations, such as authors, references, data sets, and clinical trials. License information and links to the full text are also deposited, including how to access and use content for text and data mining.

Enrichments by Crossref

We hold information that is useful to the community, and by comparing metadata we can create links between content items and add useful additional information. We current add the following additional metadata to content items:

• Member metadata to identify the organisation currently responsible for curating the metadata record.

• Reference matching: For references deposited without a DOI, we attempt to match the reference metadata to a Crossref DOI. Reference matches are included in the XML and REST APIs, including forwardLinks and getResolvedRefs (for members). We match using either an unstructured reference string or structured bibliographic metadata, depending on what is available.

• Preprint matching: We notify members who deposit preprints when we find an article that matches their preprint. They can add this to the metadata record. Matching is based on the article title and authors.

External sources

We use a small number of trusted, external organisations to supplement member-deposited metadata. This is useful in cases where members do not provide certain types of metadata, either because they don’t have the full information or their systems aren’t able to process and send it to us.

We currently have the following sources:

• Retraction Watch, a non-profit organisation that collects and curates retractions. Their database of retractions has been acquired by Crossref and made publicly available. Retractions from Retraction Watch are included in REST API works and the full database is available as a download in csv format.

Licensing

Almost all of the metadata we hold is reusable without restriction, with the exception of abstracts which are subject to publisher or author copyright. The majority of metadata is considered to be ‘facts’ which are not copyrightable and are thus in the public domain (CC0). The agreement we have with our members permits us to distribute abstracts, but they retain the license under which they were published. We release any Crossref-generated data, including aggregations, as public domain material. In summary:

Summary of services

The following sections give an overview of our services. Use the links or navigation on the left for further details, examples, and full documentation.

User interfaces

User interfaces are designed for real people to retrieve metadata in human-readable formats.

APIs

Interfaces for computers to retrieve metadata in a structured format. We provide APIs that return JSON and XML formats. We recommend the REST API for most users: it offers the most flexibility and features, and uses JSON format which is simpler to interpret than XML.

Bulk downloads

We offer access to all of our metadata as bulk downloads for free. These are useful for high volume, complex research and analysis tasks that can’t be completed easily via an API.

For members

Some services are specifically to support members checking their deposited metadata.