What is a persistent identifier (PID)?

Last updated: 2026-03-31

A persistent identifier, or PID, is a stable and unique reference assigned to a digital object such as a publication, data set, or other digital resource that remains valid indefinitely. A PID may also act as an authoritative reference to concepts or real world phenomena such as individuals, organisations or samples, represented by digital objects and metadata. PIDs play a crucial role in sustainable scholarly communication.

Unlike ordinary links or URLs, which may break or change over time, persistent identifiers are designed to endure. They rely on digital infrastructures that map the identifier to the resource’s current location. Because PIDs are created to be resolvable online, users can reliably access the resource by always using the identifier, ensuring continuous availability, discoverability, and citation.

Some PID systems will provide a stable reference to a digital object, but do nothing else. Other PID systems may have additional features, such as making it possible to describe the object with metadata that is disseminated together with the PID.