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:

  • Notifications of new matching records
  • ‘Snapshots’ of data to download
  • Priority support

We are very excited to start our new Plus service and invite you to explore below new features, including alerts of new matching records along with pricing, 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.


When is the new service available?

Plus service starts January 2018.

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.

Does the new agreement replace my existing one?

Yes, if you are using OAI-PMH, the new agreement replaces your existing one.

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

OAI-PMH may be accessed using the following:

  1. A Crossref-provided token
  2. Up to 2 IPs/ranges
  3. Up to 2 CIDRs

The REST API is accessed using a Crossref-provided token.

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 bulk downloads, based on a select set of parameters (e.g. journal, year, etc.) for:

  • The entire archive
  • Some large set of it

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.

Crossref may place limits on the number or size of reports.

Full feature development is expected in 1Q18. Prior to this, full archives will be available in XML and JSON.

Filters based on commonly used data are in development:

  • ISSN
  • Month & year
  • Publisher
  • Journal title


Alerts may be requested by users, to receive notifications when new records or updates are deposited in the Crossref system matching a select set of parameters.

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

Notifications communicate matching records but do not themselves contain metadata records.

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 50 requests per rate limit window, then it allows 50 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.


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