Some of you who have submitted content to us during the first two months of 2021 may have experienced content registration delays. We noticed; you did, too.
The time between us receiving XML from members, to the content being registered with us and the DOI resolving to the correct resolution URL, is usually a matter of minutes. Some submissions take longer - for example, book registrations with large reference lists, or very large files from larger publishers can take up to 24 to 48 hours to process.
TL;DR: We have a Community Forum (yay!), you can come and join it here: community.crossref.org.
Community is fundamental to us at Crossref, we wouldn’t be where we are or achieve the great things we do without the involvement of you, our diverse and engaged members and users. Crossref was founded as a collaboration of publishers with the shared goal of making links between research outputs easier, building a foundational infrastructure making research easier to find, cite, link, assess, and re-use.
Event Data uncovers links between Crossref-registered DOIs and diverse places where they are mentioned across the internet. Whereas a citation links one research article to another, events are a way to create links to locations such as news articles, data sets, Wikipedia entries, and social media mentions. We’ve collected events for several years and make them openly available via an API for anyone to access, as well as creating open logs of how we found each event.
2020 wasn’t all bad. In April of last year, we released our first public data file. Though Crossref metadata is always openly available––and our board recently cemented this by voting to adopt the Principles of Open Scholarly Infrastructure (POSI)––we’ve decided to release an updated file. This will provide a more efficient way to get such a large volume of records. The file (JSON records, 102.6GB) is now available, with thanks once again to Academic Torrents.
The collective power of our members’ metadata is available to use through a variety of tools and APIs—allowing anyone to search and reuse the metadata in sophisticated ways.
Members register content with us to let the world know it exists. They send us information called metadata which we collect and store in a standard way. We make this metadata openly available via our APIs, which means people and machines can incorporate it in their research tools and services. Learn more about the metadata each member is depositing with us using our Participation Reports.
Manuscript tracking services, search services, bibliographic management software, library systems, author profiling tools, specialist subject databases, scholarly sharing networks - all of these (and more) incorporate scholarly metadata into their software and services. They use our free APIs to help them get the most complete, up-to-date set of metadata from all of our publisher members. And of course, members themselves are able to use our free APIs too.
Watch the introductory animation in your language:
To retrieve metadata from Crossref, you do not need to be a member. We have various options for retrieving metadata - some are more suitable for human use, and some for machine use.
Here is a comparison of the metadata retrieval options. Please note that all interfaces include Crossref test prefixes: 10.13003, 10.13039, 10.18810, 10.32013, 10.50505, 10.5555, 10.88888.
Feature / option
Metadata Search
Simple Text Query
REST API
XML API
OAI-PMH
OpenURL
Metadata Plus (OAI-PMH + REST API)
Interface for people or machines?
People
People
People (low volume and occasional use) and machines
If you’d like to share a case study for how you use Crossref metadata, and be featured on our blog, please contact us.
Using content negotiation
The APIs listed here provide metadata in a variety of representations (also known as output formats). If you want to access our metadata in a particular representation (for example, RDF, BibTex, XML, CSL), you can use content negotiation to retrieve the metadata for a DOI in the representation you want. Content negotiation is supported by a number of DOI registration agencies including Crossref, DataCite, and mEDRA.
Obligations and fees for metadata retrieval
It is important that members understand that metadata is used by other software and services in the Crossref community. We encourage members to submit as much metadata as possible so that our APIs can include and deliver rich contextual information about their content.
If you’re using the public REST API, it is optional but encouraged to include your email address in header requests as this puts your query into the “polite” pool which has priority processing. Learn more about our REST API etiquette.
Crossref generally provides metadata without restriction; however, some abstracts contained in the metadata may be subject to copyright by publishers or authors.
How to participate - interfaces for people
Crossref provides a number of user interfaces to access Crossref metadata. Some are general-purpose, and others are more specialized.
Metadata Search is our primary user interface for searching and filtering of our metadata. It can be used to look up the DOI for a reference or a partial reference or a set of references, to look up metadata for a content item, submit a query on an author’s name, or find retractions registered with us. It can also be used to search and filter a number of elements, including funding data, ISSN, ORCID iDs, and more.
Simple Text Query is a tool designed to allow anyone to look up DOIs for multiple references. As such it’s particularly useful for members who want to link their references. Members can even use this tool to add linked references to their metadata.
How to participate - APIs for machines
We have a number of APIs for accessing metadata. There is one general-purpose API and several specialized ones. The specialized APIs are designed for our members so that they can manage their metadata or they are APIs based on standards that are popular in the community.
This API lets you look up a Crossref DOI for a reference, using a standard that is popular in the library community, and particularly with link resolver services.
This API outputs in XML and uses a standard popular in the library community to harvest metadata. The OAI-PMH API is optimized to return a list of results matching the query parameters (such as publication year). The OAI-PMH API is included in the Metadata Plus service.
We support a range of tools and APIs to help you get metadata (and identifiers) out of our system. Some query interfaces will return only one match, and only if fairly strict requirements are met. These interfaces may be used to populate citations with persistent identifiers. Other interfaces will return a range of results and may be used to retrieve a variety of metadata records or match metadata when metadata, DOIs, or other identifiers (such as ORCID iD, ISSN, ISBN, funder identifier) are provided.
User interfaces
Metadata Search - any results containing the entered search terms will be returned. Search by full citation, title (or fragments of a title), authors, ISSN, ORCID, DOI (to retrieve metadata) and more.
Simple Text Query - cut-and-paste your reference list into the form and retrieve exact DOI matches.
APIs
REST API - a RESTful API that supports a wide range of facets and filters. By default, results are returned in JSON, and returning results in XML is an option. This API is currently publicly available (no account or token required), but there is a paid Metadata Plus service available on a token for those who require guaranteed service levels
XML API - the XML API will return a DOI that best fits the metadata supplied in the query. This API is suitable for automated population of citations with DOIs as the results are accurate and do not need evaluation. This API is available to members, or by supplying an email address.
OpenURL - used mostly by libraries but also available to members, or by providing an email address. Learn more about OpenURL access.
OAI-PMH - as well as a free public list option, we provide a subscription-only OAI-PMH interface that may be used to retrieve sets of metadata records (subscribers only)
GetResolvedRefs - retrieve DOIs matched with deposited references (members only)
Deposit harvester - retrieve DOIs and metadata for a given member (members only).
