A Digital Object Identifier (DOI) is a persistent, globally unique character string that identifies a digital object — most often a journal article, dataset, book or other research output — and reliably resolves to that object’s current location on the web. Unlike a plain URL, a DOI is designed to keep working even when the underlying web address changes, because the identifier points to a record that the owner keeps up to date rather than to a fixed server path.
DOIs are governed by ISO 26324, the international standard that defines DOI syntax and the rules of the DOI system, and they are managed at the apex by the International DOI Foundation (IDF). This article explains what a DOI is, how it is structured, how resolution works through the Handle System, and which organisations assign DOIs in scholarly publishing.
The structure of a DOI: prefix and suffix
Every DOI has two parts separated by a forward slash. A prefix always begins with 10. followed by a registrant code identifying the organisation that registered the DOI (for example 10.1000). A suffix, chosen by the registrant, identifies the specific item and can be any string the registrant chooses, provided it is unique within that prefix.
| Component | Example | Meaning |
|---|---|---|
| DOI prefix | 10.1000 | Directory indicator (10) plus registrant code |
| DOI suffix | 182 | Registrant-assigned identifier for the object |
| Full DOI | 10.1000/182 | The complete, opaque identifier |
| Resolvable form | https://doi.org/10.1000/182 | The DOI expressed as a clickable link |
The DOI itself is deliberately opaque: the characters carry no built-in meaning about the content, the publisher or the year. This opacity is a feature, not a flaw — it means a DOI never has to change because something about the object changed. The recommended way to display a DOI is as a full HTTPS link using the https://doi.org/ proxy, so that readers can simply click it.
How DOI resolution works: the Handle System
The technical machinery beneath every DOI is the Handle System, a distributed identifier-resolution infrastructure developed by the Corporation for National Research Initiatives. A DOI is in fact a Handle within a specific namespace, and DOI resolution is the process of looking up the identifier and returning the current data associated with it — principally the URL where the object now lives.
When you click https://doi.org/10.1000/182, the request reaches the DOI proxy server, which queries the Handle System for that DOI’s record. The record contains the up-to-date target URL, and the resolver redirects your browser there. Because publishers update the target URL when content moves, the DOI keeps resolving even after the destination has been reorganised — this is the core of persistence.
Persistence versus ordinary URLs
An ordinary web link breaks — the familiar “404 Not Found” — whenever a page is moved, a domain is retired or a site is restructured. This phenomenon, known as link rot, is corrosive to the scholarly record, which depends on being able to cite and re-find sources years or decades later. A DOI mitigates this by adding a layer of indirection: citations point at the stable identifier, and the identifier’s owner maintains the mapping to wherever the content actually resides. The DOI is part of a wider family of persistent identifiers (PIDs) explored across our persistent-identifiers coverage.
Who assigns DOIs?
The IDF does not register individual DOIs itself; instead it appoints DOI registration agencies that serve particular communities. In scholarly publishing the two largest are Crossref, which registers DOIs for journal articles, conference papers, books and other text-based scholarly content, and DataCite, which focuses on research datasets and other non-traditional outputs. Each agency collects descriptive metadata alongside the DOI and operates the services that make DOIs useful for discovery and citation. We examine that division of labour in our piece on Crossref and the DOI registration agencies.
DOIs also coexist with other identifiers in the modern research infrastructure — ORCID for people, ROR for organisations, RAiD for projects — described in our overview of ORCID, ROR, RAiD and the DOI in 2026. For definitions of these and related terms, the CASRAI dictionary is a useful reference.
Versioning and DOIs
Because a DOI is permanent, an updated version of a dataset or preprint is usually given its own DOI, with a separate “concept” DOI that always points to the latest version. This pattern is explained in our article on concept and version DOIs.
Frequently asked questions
Is a DOI the same as a URL?
No. A DOI is an identifier, not a location. It is usually expressed as a URL via the https://doi.org/ proxy so it can be clicked, but the identifier itself is the part after the proxy. The URL it points to can change; the DOI does not.
What standard defines DOIs?
DOI syntax and the rules of the DOI system are defined by ISO 26324. The system is administered by the International DOI Foundation, and resolution is provided by the Handle System.
Can a DOI ever stop working?
A DOI continues to resolve as long as its registration agency and the registrant maintain the record. The persistence guarantee is a social and contractual commitment as well as a technical one: it depends on publishers updating target URLs and on the agencies remaining operational.
How do I cite a DOI correctly?
Best practice is to present the DOI as a full HTTPS link, for example https://doi.org/10.1000/182, so that it is both human-readable and machine-actionable. Guidance for authors is collected on our for-authors page.