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

``LicenseRef-`` and ``AdditionRef-`` Prefixes
=============================================

Not all license texts are present on the SPDX License List. The SPDX legal team uses the `SPDX License Inclusion Principles <https://github.com/spdx/license-list-XML/blob/main/DOCS/license-inclusion-principles.md>`__ to evaluate whether particular license and exception texts are appropriate to add to the List.

To represent a license that is *not* on the License List, you can create a custom identifier using a ``LicenseRef-`` prefix.

For example:

``# SPDX-License-Identifier: LicenseRef-MyLicense``

indicates that the content is subject to a license whose text is *not* on the SPDX License List.

``# SPDX-License-Identifier: MIT WITH AdditionRef-MyExtraRequirement``

indicates that the content is subject to the MIT license, with additional text that is *not* on the SPDX License List.

More details on the formatting for ``LicenseRef-`` and ``AdditionRef-`` syntax can be found in the `SPDX License Expression Syntax <https://spdx.github.io/spdx-spec/v3.0.1/annexes/spdx-license-expressions/>`__.

Of course, because the license text or addition text is *not* on the SPDX License List, you will likely still need to communicate to the recipient which specific text corresponds to the custom identifier. Practices such as the `FSFE REUSE Software specification <https://reuse.software/spec-3.3/>`_ can be helpful in defining standard locations to include license text in your repository.