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Learn About EZID

What Is EZID?

What is EZID?

EZID is a service and a platform provided by the California Digital Library for creating, registering, and managing persistent identifiers for scholarly research and cultural heritage objects, including but not limited to articles, datasets, images, and specimens.

Persistent identifiers are the backbone of scholarly communication infrastructure. As more knowledge circulates online, persistent identifiers are increasingly needed to help to disambiguate scholarly objects, to make these objects discoverable, shareable, and citable by both humans and machines, and to support long-term preservation and access. Persistent identifiers facilitate networked research environments, enable more robust measurement of scholarly outputs, and confer scholarly credibility.

EZID is a crucial piece of infrastructure that provides a streamlined, low-cost, and high-quality persistent identifier service for libraries, museums, research groups, and publishers.

EZID currently supports two types of commonly used identifiers: Digital Object Identifier (DOI) and Archival Resource Key (ARK). DOI services are available for University of California users only.

EZID offers a user interface and robust API and supports automated workflows standards-based processes.

Current Users

"The partnership between EZID and Crossref presents an exciting opportunity for eScholarship and our journal partners. The inclusion of our Open Access publications in new discovery services via Crossref, particularly its metadata feed, will dramatically increase the exposure of the important scholarship published on our platform."

Current users

EZID users include University of California campuses and administrative units as well as non-UC institutions. EZID's DOI services are available for University of California users only. ARK services are available for both UC and non-UC users.

University of California partners


University of California

University of California libraries sponsor free EZID memberships for their campuses. Contact your librarian to request an account for your department or group.

ARK Pricing: Education and Non-Profit

  • Annual subscription fee
  • Includes creation and maintenance of up to 1 million identifiers per year
Pricing Schedule ARKs
Assoc/Bac Granting Institution* $300
Masters Granting Institution* $600
Research Institution or Non-Profit Organization* $1,500
Research group, department, or team $500

ARK Pricing: For-Profit Organizations

  • Annual subscription fee
  • Includes creation and maintenance of up to 1 million identifiers per year
Pricing Schedule ARKs
Small (less than 100 employees) $1,500
Medium (100 to 500 employees) contact us
Large (over 500 employees) contact us

* Consortium (3 or more institutions or organizations) 20% discount on any fee marked

For any questions regarding the above categories or rates, please contact us.

University of California researchers: please contact us for UC rates.


Non-technical Documentation

What is a long-term identifier?

An identifier is an association between a character string and an object. Objects can be files, parts of files, names of persons or organizations, abstractions, etc. Objects can be online or offline. Character strings include URLs, serial numbers, names, addresses, etc. A "persistent identifier" is an identifier that is available and managed over time; it will not change if the item is moved or renamed. This means that an item can be reliably referenced for future access by humans and software. EZID currently supports persistence for two kinds of identifiers: DataCite Digital Object Identifiers (DOIs) and lower-cost Archival Resource Keys (ARKs).

What is a DOI?

DOI stands for "Digital Object Identifier." It is an identifier originating from the publishing world and in widespread use for journal articles. DOIs become persistent when the objects and identifier forwarding information are maintained.

What is an ARK?

ARK stands for "Archival Resource Key." It is an identifier originating from the library, archive and museum community. ARKs become persistent when the objects and identifier forwarding information are maintained.

Can DOIs and ARKs be used together?

ARK identifiers have certain features that can be very useful for:

  • Keeping track of many granules of a dataset (ARKs will be able to "pass through" a suffix, so many thousands of items can be referenced on the basis of a single registration);
  • Keeping track of data before a decision has been made about whether or not it is going to be retained (ARKs can be deleted).

This can make it attractive to use ARKs during the early part of a dataset's "life" or the early stages of the research process. Then, when the time comes to begin writing up results and it becomes clear which object(s) will be cited, it may appropriate to get DOIs for those objects.

DOIs have the citation-level "reputation" and it is possible to use the ARK of the cited object as the "suffix" for the DOI so that there is a traceable connection between the two. Here is what that means:

Step 1. You assign an ARK to a resource for good management and tracking: ark:/99999/fk4sf2w65j

Step 2. You decide to cite the resource, so you want a DOI.

Step 3. Using either the Advanced Create UI or the API, request a doi with this form: doi:10.5072/FK2fk4sf2w65j

In this way, the two identifiers have a relationship, so the object can be tracked throughout its life cycle. With EZID, clients get access to both of these identifiers and can take best advantage of both approaches.

What is identifier resolution?

Instead of leading directly to an object, one identifier frequently points to another, or "target URL", that leads directly to the object. The process of getting to the final target name, possibly via a chain of intermediate names, is called "resolution." Resolution on the web is usually fast and invisible. It is done behind the scenes on your behalf by web browsers. Unsuccessful resolution, however, usually means visible failure to access the object that you were expecting, resulting in a "broken identifier." Objects tend to move, so identifier persistence depends on resolution using up-to-date target URLs. To make this happen, EZID provides a way for people to update target URLs as they change when objects move around. This is very similar to leaving a forwarding address when you change your residence. As the starting point for resolution, the resolver effectively lets you publicize an unchanging identifier that you maintain so that it will consistently hit a target that may be moving. EZID currently updates two resolvers: N2T (Name-to-Thing) based at and the DOI (Digital Object Identifier) resolver based at

What is metadata?

Metadata is information (data) about the object, such as the name of the object's creator, the date of creation, the target URL, the version of the object, its title, and so on. EZID allows the user to enter metadata at the same time as an identifier is requested. Associating metadata with identifiers enables more sophisticated mechanisms for digital content discovery and higher-level assurances of long-term persistence.

Who should I contact for more information?

Please contact us with any questions or comments. Also, see Identifier Basics for more information about the identifier practices implemented by the EZID team.

EZID Service Guidelines

Technical Documentation

API Documentation

OAI-PMH Service Documentation

Identifier Basics

Open Source Software for EZID

Suffix Passthrough Explained

Status Information

For information about the status of the EZID system, please consider the following options:

API inquiries

The CDL System Status Page

The EZID Status Blog

The RSS Feed from the Status Blog


Can EZID identifiers be related to the links in other systems?

EZID identifiers can be related to external links if you associate them with metadata, for example by using the relatedIdentifier field in the DataCite metadata schema.

What is the best way to link to the DOIs and ARKs I create with EZID?

If you would like to include clickable links to DOIs and ARKs on a landing page, we recommend that you format them following this html template:

DOI: <a href="">doi:10.1234/ABCD</a>
ARK: <a href="">ark:/12345/abcde</a>
We discourage the practice of publishing or citing links to identifier management pages at because it is generally preferable for search engine crawlers to index resource (object) pages rather than pages of identifier administration details. In this way, users looking for data will be sure to find the landing pages you have prepared.

We have a DSpace repository. Is it possible (or advisable) to apply EZID identifiers retrospectively or in the future for the content in our Dspace repository?

Because EZID has an API, it is possible to write code to interact with your Dspace repository.

What happens when an account holder leaves our institution? Can this account holder still update the DOI or ARK? If not, what must happen?

If an account-holder leaves your institution, please let us know so that we revoke their CREATE access to EZID. They will continue to be able to maintain all existing identifiers.

What if research partners are not at our institution? Can they also use EZID for a project partially based at our institution?

If there is a researcher from your institution associated with the project, and if you want to sponsor the access, then we are okay with extending access. Please use the sponsored account order form (see above) to request the new account.

DOI Services FAQs

ARKs in the Open FAQs


Webinars and Presentations


EZID and N2T at CDL Presentation at UC DLFx, February 27, 2018

Four Unsolved Problems (with Persistent Identifiers) Presentation at PIDapalooza, Palau de Congressos de Girona, Spain, January 23, 2018

Compact Identifiers for Data Citation in Biomedicine and Beyond Presentation at PIDapalooza, Palau de Congressos de Girona, Spain, January 23, 2018

DOI service providers: 4 factors to consider


Software Citation Principles Presentation at DataCite Strategy Meeting (slides), April 3, 2017

Identifiers and Citation: Frequently Asked Questions Presentation at California Data Librarians conference (slides), March 14, 2017

Identifiers and Citation Webinar for CENDI (slides), Feb. 15, 2017


Customizable materials

EZID Postcard for STEM outreach

EZID Postcard for Digital Humanities outreach

API Guide