Latest blog posts
Helena Cousijn
2025 November 19

Crossref at the Frankfurt Book Fair 2025

The Frankfurt Book Fair is the largest book fair in the world, and therefore a key event on our calendar. Held annually in Frankfurt, Germany, the 77th Frankfurt Book Fair (October 15–19, 2025) saw 118,000 trade visitors and 120,000 private visitors from 131 countries. The Crossref booth was located, as usual, in Hall 4.0 where all the stands with information about academic publishing can be found. Four Crossref colleagues attended the Book Fair this year, and in this blog post, you can read more about their meetings, experiences, and plans. 

...Find out more
Lena Stoll
2025 November 06

The sunset is on the horizon for Metadata Manager. What's next?

TL;DR. Metadata Manager will be retired at the end of 2025. Over the past four years, we have been developing a new helper tool to replace it, and that tool has now reached a stage of maturity that means we will be able to switch off Metadata Manager by the end of the year.

...Find out more
Martyn Rittman
2025 November 05

Announcing changes to REST API rate limits

Our REST API makes all of the metadata we hold publicly available. It receives the majority of our API traffic, with around 1 billion hits per month. It’s one of the key ways that we fulfil our mission to make research objects easy to find, cite, link, assess, and reuse. From 1 December 2025, we will be revising the rate limits for the public and polite pools of the REST API to ensure that we can maintain a stable and reliable system, and that metadata is freely available to everyone.

...Find out more
Johanssen Obanda
2025 November 04

Celebrating Noyam Journals’ Metadata Award

Noyam Journals, based in Accra, Ghana, was recently recognised for the completeness of its metadata through the Crossref Metadata Award, part of our 25th anniversary celebrations. Noyam was one of six publishers worldwide to receive the award and stood out as a leader among members of our Global Equitable Membership (GEM) Program.

...Find out more
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Documentation

API Versions

REST API Versions

The Crossref REST API is versioned. You should always use the API version in your REST API requests.

Breaking changes

Any breaking changes will be released in a new API version. Breaking changes are changes that can potentially break an integration. Breaking changes include:

  • removing an entire operation
  • removing or renaming a parameter
  • removing or renaming a response field
  • adding a new required parameter
  • making a previously optional parameter required
  • changing the type of a parameter or response field
  • removing enum values
  • adding a new validation rule to an existing parameter
  • changing authentication or authorization requirements

Non-breaking changes

Any additive (non-breaking) changes will be available in all supported API versions. Additive changes are changes that should not break an integration. Additive changes include:

  • adding an operation
  • adding an optional parameter
  • adding an optional request header
  • adding a response field
  • adding a response header
  • adding enum values

Specifying an API version

To be safe, specify an API version in your requests.

For example:

https://api-crossref-org.turing.library.northwestern.edu/v1/works?rows=0

However, as long as v1 of the API exists, requests that do not contain an API version in the request will default to v1. Eventually, if you specify an API version that is no longer supported, you will receive a 400 error.

Upgrading and legacy support

When a new REST API version is released, the previous API version will be supported for 24 more months following the release of the new API version. In exceptional circumstances, we may decide to extend this.

Before upgrading to a new REST API version, you should read the changelog of breaking changes for the new API version to understand what breaking changes are included and to learn more about how to upgrade to that specific API version.

Supported API versions

The following REST API versions are currently supported:

  • V1

Credits: This policy is adapted from the very short, clear and reasonable Github API policy

Page maintainer: Martyn Rittman
Last updated: 2022-December-01