Digital object identifier

A DOI is a character string that permanently identifies an electronic document or other digital object. Unlike URLs, which can change or break, a DOI is a persistent identifier that remains stable even if the object's location changes. The system is built on the Handle System, developed by the Corporation for National Research Initiatives, which provides a resolution mechanism that maps a DOI to the object's current location. The primary purpose is to enable reliable citation and access to digital content, particularly in scholarly communication, where stable links are essential for academic integrity. DOIs also support metadata management, allowing for the exchange of information about the object, such as authorship, publication date, and publisher.

A DOI consists of a prefix and a suffix, separated by a slash, for example, 10.1000/xyz123. The prefix is a unique number assigned to a registrant (e.g., a publisher) by a registration agency, starting with '10.' to distinguish it from other Handle System identifiers. The suffix is chosen by the registrant and can be any alphanumeric string, often incorporating existing identifiers like ISBNs or internal codes. The syntax is defined by ISO 26324, which specifies that a DOI is case-insensitive and does not include spaces. The system also supports Unicode, allowing for non-Latin characters. The resolution process uses the Handle System's infrastructure, which ensures that the DOI remains functional even if the registrant changes.

DOIs are most commonly used in academic publishing, where they are assigned to journal articles, conference papers, and books, enabling persistent linking and citation metrics. They are also used for datasets, software, and other research outputs, particularly through DataCite, which encourages data sharing and citation. Beyond academia, DOIs are used by government agencies, such as the U.S. Government Publishing Office, to provide stable access to official documents. In the entertainment industry, DOIs have been used for video content, and in the cultural heritage sector, they help identify digital surrogates of artworks. The system is also employed in scientific data repositories, such as those at NASA and the European Space Agency, to ensure long-term access to research data.

One lesser-known aspect is that DOIs are not only for digital objects; they can also identify physical objects, such as books or even people, though this is less common. The DOI system supports multiple resolution, allowing a single DOI to point to different versions of an object, such as a preprint and a published article. Another niche application is in the field of legal publishing, where DOIs are used for court decisions and legislation, as seen in some European countries. The system also has a 'metadata' feature that allows for the retrieval of structured information about the object, which is used in automated citation processing. Additionally, the International DOI Foundation has developed a 'DOI Content Negotiation' feature that enables the delivery of different formats of the object based on the requester's preferences.

Handle System

A general-purpose distributed information system that provides persistent identification and resolution of digital objects; the underlying technology for DOIs.

Registration agency

An organization authorized by the International DOI Foundation to assign DOIs and provide services to registrants, such as Crossref and DataCite.

Persistent identifier

A long-lasting reference to a digital object that remains stable and resolvable over time, unlike a URL.