Archival Resource Key

An Archival Resource Key (ARK) is a multi-purpose URL suited to being a persistent identifier for information objects of any type. It is widely used by libraries, data centers, archives, museums, publishers, and government agencies to provide reliable references to scholarly, scientific, and cultural objects. In 2019 it was registered as a Uniform Resource Identifier (URI).[1]

Archival Resource Key
OrganisationARK Alliance
Introduced2001 (2001)
No. issued8.2 billion
No. of digitsvariable
Check digitNCDA, optional

A URL that is an ARK is distinguished by the label ark: after the URL's hostname, which sets the expectation that, when submitted to a web browser, the URL terminated by '?' returns a brief metadata record, and the URL terminated by '??' returns metadata that includes a commitment statement from the current service provider. The ARK and its inflections ('?' and '??') provide access to three facets of a provider's ability to provide persistence.

Implicit in the design of the ARK scheme is that persistence is purely a matter of service and not a property of a naming syntax. Moreover, that a "persistent identifier" cannot be born persistent, but an identifier from any scheme may only be proved persistent over time. The inflections provide information with which to judge an identifier's likelihood of persistence.

ARKs can be maintained and resolved locally using open source software such as Noid (Nice Opaque Identifiers) or via services such as EZID. Most implementations are decentralized and no fees are charged for the right to assign ARKs. Some implementations choose to publish ARKs via the centralized N2T (Name-to-Thing) resolver.