With the increasing digitization of research and teaching, the number of software programs developed and used at scientific institutions is also rising. In the context of research data management in particular, the provision of the corresponding software is of central importance for the traceability, reproducibility, and reuse of scientific results.

The unique identification of software using persistent identifiers (PIDs) is therefore an essential step in making software visible, citable, and sustainably usable as an independent research result. PIDs enable permanent referencing, link software to the associated publications, data, and projects, and thus promote transparent, open science.

Which PIDs are used – and where are they available?

• DOI (Digital Object Identifier)
  A DOI is often assigned to published software – e.g., via a connection from GitHub to Zenodo or when publishing in a repository. Software repositories offer standardized metadata, version control, and long-term archiving.
• SWHID (SoftWare Hash IDentifiers)
  The SWHID is an identifier developed specifically for software that makes each version of a software object uniquely referenceable down to the source code level. It is particularly suitable for the precise documentation of software artifacts. It is assigned in repositories such as Software Heritage, among others. A dedicated  working group is responsible for the development and management of the SWHID.
• ARK (Archival Resource Key)
  The ARK is used for permanent referencing and archiving of software, especially in institutional and long-term archiving contexts. To register ARKs, an institution must contact the ARK Alliance.
• Handle
  The Handle system is a universal identification system that is used in particular in some research information systems and data repositories. Handles can also be assigned to software objects. An institution can set up its own handle server or use a service such as ePIC.
• URN (Uniform Resource Name)
  URNs are mainly used in libraries and institutional repositories, e.g., for open source software or documentation. In Germany, the German National Library (DNB) is responsible for this.

The assignment of PIDs for software plays a key role in documenting scientific software developments, making them retrievable, and keeping them permanently accessible—an important building block for open, networked, and reproducible research.

A summary of our online workshop on PID for software held on June 30, 2025, has been published on our blog.