.. SPDX-License-Identifier: CC-BY-4.0
   Copyright 2026 The Linux Foundation

Format
======

Short-form License IDs
----------------------

To add an SPDX short-form license ID to your code, add a line in the following form, using whatever comment format applies to that file's language, e.g.:

* ``// SPDX-License-Identifier: MIT``
* ``/* SPDX-License-Identifier: MIT OR Apache-2.0 */``
* ``# SPDX-License-Identifier: GPL-2.0-or-later``

Very specifically, this consists of the following parts on *one line*:

1. (if required) The 'begin comment' characters for the applicable programming language (``/*``, ``//``, ``#``, ...)
2. The characters ``SPDX-License-Identifier:`` with whitespace following the colon
3. An SPDX license ID (e.g., ``Apache-2.0``) or SPDX license expression (see below)
4. (if required) The 'end comment' characters for the applicable programming language (``*/``, ...)

The identifiers for these short-form license statements come from the `SPDX License List <https://spdx.org/licenses>`__.

Combinations of Multiple Licenses
---------------------------------

Many projects include code that is under more than one single license. In fact, many individual files may contain code that is covered by multiples licenses.

The `SPDX License Expression Syntax <https://spdx.github.io/spdx-spec/v3.0.1/annexes/spdx-license-expressions/>`__ defines a few operators that can be used to construct expressions with more than one license. These are described on the following pages.