OAI resolver
What is an OAI identifier?
There is a need for globally unique decentralised persistent identifiers (PIDs) for identifying research outputs resolvable to repositories.

An OAI (Open Archives Initiative) identifier is a unique identifier of a metadata record. OAI identifiers are used in the context of repositories using the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH), however, the process by which they are assigned can be, in principle, used more broadly elsewhere.


oai:oro.open.ac.uk : 73739
globally unique OAI Prefix locally unique identifier

In comparison to DOIs, OAI identifiers are registered in a distributed rather than centralised manner and there is therefore no cost for minting them. OAI identifiers are persistent identifiers in repositories that declare their level of support for deleted documents in the deletedRecord element of the Identify response as persistent. CORE recommends repositories to provide this persistent level of support.

There is no strict format for the identifier apart from it having to be a URI, but a good practice is for it to consist of a globally unique prefix identifying the repository and a suffix that is locally unique to a given metadata record in the repository.

The following are examples of OAIs available in CORE

Why do we need OAI identifiers?

OAI Identifiers are viable PIDs for repositories that can be, as opposed to DOIs, minted in a distributed fashion and cost-free, and which can be resolvable directly to the repository rather than to the publisher.

This approach has the potential to increase the importance of repositories in the process of disseminating knowledge. CORE provides a global OAI Resolver built on top of the CORE research outputs aggregation system.

OAI identifiers do not replace DOIs, but complement them. According to the DOI handbook “Uniqueness (specification by a DOI name of one and only one referent) is enforced by the DOI system. It is desirable that two DOI names should not be assigned to the same thing.” A DOI typically identifies the canonical final version of record (VoR) of a paper. An OAI Identifier a metadata record in a repository. As there often exist multiple copies of a paper across repositories, it is, in fact, desirable that these records identified using an OAI Identifier are linked to a single DOI.
OAI Resolver

CORE provides a global resolver for OAI identifiers at

The RESTful call to resolve an OAI is available at:

As CORE aggregates data from repositories from across the globe, it is aware of OAI Identifiers for each repository record across this network. This means that repositories do not need to do anything to register their OAI identifiers to allow the OAI resolver to work on their records apart from making sure that they expose their metadata using OAI-PMH, which is a widely supported functionality.

However, we recommend that repositories register for the CORE Repository Dashboard to check that their metadata records are harvested correctly in their entirety. This is an extremely low barrier to adoption with the resolver effectively working out-of-the-box.

CORE can resolve any OAI identifier to either a metadata page of the record in CORE or route it directly to the repository page. To route redirection directly to the repository, it is necessary to provide mapping in the CORE Repository page between the OAI prefix of a repository and the currently used URL for the repository metadata record display page/splash. The redirection will change instantly.

Find out more in our Open Repositories 2022 article.

OAI base URL looks similar to http://journaldomain.com/cgi/oai2 or http://journaldomain.com/oai/request when homepage URL is http://journaldomain.com. CORE cannot harvest the journal’s/repository’s content via its webpage URL. If you are not sure whether your journal/repository has an OAI base URL, contact our team and we will provide technical support to you.

A more technical answer for https://support.core.ac.uk
Target audience: repository managers, Technical staff.

An OAI Identifier is a unique identifier which distinguishes items in a repository. It
“unambiguously identifies an item within a repository; the unique identifier is used in OAI-PMH requests for extracting metadata from the item”

The Identifier contains 3 parts, split using:
“oai“ : Unique identifier oai. This describes the type of the identifier
“website address”: Where the item is hosted.
“Unique identifier”: An identifier of the object

For example:

Not all OAI Identifiers look like this, but they are non-standard and their use is discouraged. OAI Identifiers must follow the URI (Uniform Resource Identifier) syntax. For more information about how OAI Identifiers are formed, visit Specification and XML Schema for the OAI Identifier Format.

-The item has not been harvested by CORE yet
-The repository is not yet registered as a CORE data provider. Become a provider