Metadata Plus

Metadata APIs Plus Service

The Metadata Plus service provides machine access to all our metadata records in both XML and JSON, with enhanced service and features.

For the first time, users may access multiple interfaces under one agreement, providing flexibility, robust functionality and improved support for the diverse and growing needs of the variety of organizations that use metadata in systems and services throughout scholarly communications. Enhancements include:

  • ‘Snapshot’ full-file downloads
  • Guaranteed uptime
  • Priority support

We are very excited to share our newest metadata service, called Plus, introduced in 2018. We invite you to explore below new features, including ‘snapshot’ full-file downloads,” our service commitment and more.


For subscribers, Plus provides options for query protocols and output formats, plus enhanced features and priority support.

For members, a more robust metadata delivery service supports improved content discoverability.


Why are two interfaces included? Do I have to use both?

Each interface has a different output format and uses a different protocol for retrieving records. Using both interfaces is optional, so if you’re already a subscriber, you don’t need to change what you are doing currently but you may want to take advantage of new features. We made this change so that organizations have the flexibility to choose which interface(s) to use, with access to all records in both XML and JSON, under one agreement.

How can I make sure I am getting the most from the Plus service?

Get in touch! We are happy to review the changes with you:

Description of Service

This Service Description is applicable to the Agreement terms for the Crossref Metadata APIs Plus Service only.

Service Overview

The Metadata APIs Plus Service provides metadata records for all registered content items at Crossref in XML and/or JSON, with a service level agreement and additional features described below, which together comprise the Service.

Covered Interfaces

Users may use either or both covered interfaces:


This API, for retrieving metadata in XML, uses the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH) version 2 repository framework. It uses the interface as documented at


This API, for searching and filtering metadata, is generally RESTFUL and returns results in JSON. It is documented at

Access Credentials

Access is via Crossref-provided token, which may be used for OAI-PMH and/or the REST API.

Service Level Agreement

Crossref will maintain an aggregated, average uptime for all of the interfaces that together comprise the Crossref Metadata Service of 99.5%, reported on a monthly basis. Crossref will provide technical support to Subscriber through Crossref’s existing support channels as requested by Subscriber, and will provide a response within one (1) business day to support requests received during normal working hours in the United States and the United Kingdom. “Business days” do not include weekends or legal holidays in the United States and the United Kingdom. “Response” means that support requests will be acknowledged. The time required for resolution will depend upon the nature of the request.

Additional Features

Feature Defined as Notes


User-requested full-file downloads

Data may be requested in JSON and XML via an interface separate from each API.

Pre-generated reports available via machine request and human user interface.

Filters based on commonly used data are in under consideration:

  • ISSN
  • Month & year
  • Publisher
  • Journal title

Priority Service/Rate Limits

Plus users will be prioritized via isolated resources.

Minimum number of queries per second per IP address.

Rate limiting of the API is primarily on a per access token basis. If a method allows, for example, for 75 requests per rate limit window, then it allows 75 requests per window per access token. This number can depend on the system state and may need to change. If it does, Crossref will publish it in the response headers.

Annual Fee

Please see our Fees page for pricing tiers and how we define revenue.

What’s New & Up Next

In 2018 we:

  • released snapshots downloads
  • moved fully to token access
  • rolled out our status page for an easy view into system performance

In 2019 our focus is on the ‘Sync’ feature (formerly known as Notifications):
This will allow people to update their records, for example, when citation counts change, without necessarily having to go and retrieve the entire record. More to come on this so please get in touch with Jennifer Kemp if you would like to be involved in testing or discussing any of the above, or have new things you’d like us to consider.


Each interface has extensive documentation available:

In the exceptional event that there is a release not backwards compatible, Crossref will provide extensive lead time to communicate the changes, as part of our proactive support for Plus users.

Please contact Jennifer Kemp if you would like to enquire about our Metadata APIs Plus Service.

Last Updated: 2017 October 16 by Jennifer Kemp