Explainer · Plain-language
What is a persistent identifier (PID)?
A persistent identifier (PID) is a long-lasting, globally unique reference to an entity — a person, an organisation, an output, a project — that resolves reliably to current information even as web addresses change. ORCID, DOI, ROR, and RAiD are the best-known PIDs in research.
The step most authors miss
Doing CRediT right? Don’t stop at the statement.
A CRediT statement credits you inside one paper. The recognition CRediT was built for happens when those roles are tied to you, persistently. Sign in with your ORCID — free — and claim your CRediT contributions on casrai.org, the home of the standard. They become a verified, portable part of your identity, not a line that disappears into one PDF.
Free: claim your contributions, then export a journal-ready CRediT statement, schema.org structured data, JATS XML, CSV or BibTeX — and preview your public profile. A membership publishes that profile publicly and verifies the journals you serve.
Why PIDs matter
Plain web links rot — pages move, domains lapse, and a citation can break within a few years. A PID instead points at a managed resolver that always redirects to the current location, and carries structured metadata describing the entity. This makes references durable and machine-actionable, which is why funders, publishers, and research-information systems increasingly require them.
The main PID types
ORCID identifies an individual researcher. ROR (Research Organization Registry) identifies a research organisation. DOI (Digital Object Identifier) identifies outputs such as articles, datasets, and software. RAiD (Research Activity Identifier) identifies a project or research activity over its lifetime. Each is governed by a dedicated registry that guarantees uniqueness and resolution.
The PID graph
PIDs gain value when connected: an ORCID iD links to the DOIs of a researcher's outputs, which link to the ROR of their institution and the RAiD of the funded project. This network of connected identifiers — the "PID graph" — lets systems answer questions such as "what did this funded project produce?" automatically, without manual reconciliation.
How PIDs resolve
Most research PIDs build on the Handle System or expose an HTTP resolver. Putting the identifier after the resolver prefix — for example doi.org/10.1234/abc or ror.org/02j61yw88 — returns the current landing page plus machine-readable metadata over content negotiation. The identifier itself never changes, even if the underlying resource moves.
Key facts
At a glance
- Definition: durable, unique, resolvable identifier for a research entity
- Researcher PID: ORCID
- Organisation PID: ROR
- Output PID: DOI (Crossref, DataCite)
- Activity PID: RAiD
- Value: connected "PID graph" of people, places, outputs, projects
Common misconceptions
What people often get wrong
Often heard: A persistent identifier is just a permanent URL.
Actually: No — a PID is an abstract identifier resolved by a managed service. The resolver redirects to the current URL, so the identifier stays stable even when the web address changes.
Often heard: PIDs only apply to journal articles.
Actually: No — there are distinct PIDs for people (ORCID), organisations (ROR), projects (RAiD), and many output types (datasets, software, samples), not just articles.
Going deeper
