|First published||August 2011|
|Preview version||3.0 RC|
16 May 2023
|Domain||Software bill of materials|
Software Package Data Exchange (SPDX) is an open standard for software bill of materials (SBOM). SPDX allows the expression of components, licenses, copyrights, security references and other metadata relating to software. Its original purpose was to improve license compliance, and has since been expanded to facilitate additional use-cases, such as supply-chain transparency and security. SPDX is authored by the community-driven SPDX Project under the auspices of the Linux Foundation.
The current version of the standard is 2.3.
The SPDX standard defines an SBOM document, which contains SPDX metadata about software. The document itself can be expressed in multiple formats, including JSON, YAML, RDF/XML, tag-value, and spreadsheet. Each SPDX document describes one or more elements, which can be a software package, a specific file, or a snippet from a file. Each element is given a unique ID, so that they can reference each other.
|Version number||Publication date||Notes||References|
|1.0||August 2011||The first release of the SPDX specification; handles packages.|||
|1.1||August 2012||Fixed a flaw in the SPDX Package Verification Code (a cryptographic hash function) and added support for free-form comments.|||
|1.2||October 2013||Improved interaction with the SPDX License List, and added new fields for documenting extra information about software projects.|||
|2.0||May 2015||Added the ability to describe multiple packages and the relationships between different packages and files.|||
|2.1||November 2016||Added support for describing 'snippets' of code and the ability to reference non-SPDX data (such as CVEs).|||
|2.2||May 2020||Added 'SPDX-lite' profile for minimal software bill of materials and improved support for external references.|||
|2.2.1||October 2020||Functionally equivalent to SPDX 2.2 but with typesetting for publication as an ISO standard.|||
|2.2.2||April 2022||Functionally equivalent to SPDX 2.2.1 but with spelling, grammar and other editorial improvements.|||
|2.3||November 2022||Added new fields to improve the ability to capture security related information and interoperability with other SBOM formats.|||
The first version of the SPDX specification was intended to make compliance with software licenses easier, but subsequent versions of the specification added capabilities intended for other use-cases, such as being able to contain references to known software vulnerabilities. Recent versions of SPDX fulfill the NTIA's 'Minimum Elements For a Software Bill of Materials'.
SPDX 2.2.1 was submitted to the International Organization for Standardization (ISO) in October, 2020, and was published as ISO/IEC 5962:2021 Information technology — SPDX® Specification V2.2.1 in August, 2021.
Each license is identified by a full name, such as "Mozilla Public License 2.0" and a short identifier, here "MPL-2.0".
Licenses can be combined by operators
OR, and grouping
There is also a "+" operator which, when applied to a license, means that future versions of the license apply as well. For example,
Apache-1.1+ means that
Apache-2.0 may apply (and future versions if any).
SPDX describes the exact terms under which a piece of software is licensed. It does not attempt to categorize licenses by type, for instance by describing licenses with similar terms to the BSD License as "BSD-like".
In 2020, the European Commission published its Joinup Licensing Assistant, which makes possible the selection and comparison of more than 50 licenses, with access to their SPDX identifier and full text.
Deprecated license identifiers
The GNU family of licenses (e.g., GNU General Public License version 2) have the choice of choosing a later version of the license built in. Sometimes, it was not clear whether the SPDX expression
GPL-2.0 meant "exactly GPL version 2.0" or "GPL version 2.0 or any later version". Thus, since version 3.0 of the SPDX License List, the GNU family of licenses got new names.
GPL-2.0-only means "exactly version 2.0" and
GPL-2.0-or-later means "version 2.0 or any later version".
The SPDX license identifier can be added to the top of source code files as a short string unambiguously declaring the license used. The
SPDX-License-Identifier syntax, pioneered by Das U-Boot in 2013, became part of SPDX in version 2.1. In 2017, the FSFE launched REUSE, which provides tools to validate the comment and to efficiently extract copyright information.
The SPDX license identifier is also used in a number of package managers such as npm, Python, and Rust cargo. SPDX license expressions are used in RPM package metadata in Fedora Linux, replacing the earlier use of the Callaway system. Debian uses a slightly different license specification.
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- "Joinup Licensing Assistant". Retrieved 31 March 2020.
- Richard Stallman. "For Clarity's Sake, Please Don't Say "Licensed under GNU GPL 2"!". gnu.org. Retrieved 2018-05-24.
- Jilayne Lovejoy (5 January 2018). "License List 3.0 Released!". spdx.dev. Archived from the original on 2018-01-05. Retrieved 2021-09-02.
- "Solving License Compliance at the Source: Adding SPDX License IDs - Linux Foundation". www.linuxfoundation.org.
- "package.json | npm Docs". docs.npmjs.com.
- "PEP 639 – Improving License Clarity with Better Package Metadata | peps.python.org". peps.python.org.
- "The Manifest Format - The Cargo Book". doc.rust-lang.org.
- "License: field in Spec File". Fedora Legal Documentation. Retrieved 30 July 2023.
- "Machine-readable debian/copyright file". www.debian.org.