How does Creative Commons work on Wikipedia and Wikimedia Commons?

Check the file description page. Every file on Wikipedia and Wikimedia Commons carries its own licence, chosen by the uploader from the platform's allowed list. That licence governs every downstream use of that specific file. No file may carry terms that conflict with the platform's own publishing rules. Before you reuse anything, open the description page and note the exact licence version and the named attribution parties.

Find The Licence Tag

Every file on Wikimedia Commons carries its own licence tag, visible on the description page. The uploader selects from a set that includes CC BY, CC BY-SA, CC0 and a few others. Version 4.0 International is the standard for new uploads. Older files may use versions 2.0, 2.5 or 3.0, including jurisdiction-specific ports such as CC BY-SA 3.0 Unported or CC BY-SA 3.0 Germany. The legal code URL for that specific version and port is linked from the file page. The platform does not register works or verify ownership. The uploader attests that they hold the necessary rights or that the work is in the public domain.

A file marked with the Public Domain Mark signals material believed free of known copyright restrictions worldwide, but it changes no rights. The only safe assumption is what the licence tag says, not what the thumbnail or a search filter implies.

What CC BY-SA 4.0 Demands

A file tagged CC BY-SA 4.0 requires that any reuse include the attribution parties listed on the file page. That list normally states the author and the source URL. The ShareAlike condition applies: if you create adapted material from that file and share it, you must license the adapted material under CC BY-SA 4.0 or a license Creative Commons has formally named compatible. The official compatibility list controls. Do not assume two SA licences are compatible. CC BY-SA 4.0 and CC BY-SA 3.0 are not automatically compatible for adaptations, though the community often treats them as such in practice, the legal code does not.

Satisfy The Attribution Requirement

When you reuse a file from Wikimedia Commons under a BY or BY-SA license, you must retain the creator, a copyright notice, a notice referring to the license, a warranty disclaimer, and a URI or hyperlink to the material where reasonably practicable. Indicate modifications and retain earlier modification notices. The 4.0 legal code does not separately require the work's title, though including it is useful. Attribute in any reasonable manner for the medium. For a website, place a credit line under the image with a hyperlink to the original file page and a hyperlink to the exact deed or legal code. For a printed book, a credits page with the same information works, provided the mapping from each image to its credit is clear and the credit remains readily accessible.

When ShareAlike Kicks In

The ShareAlike condition triggers only when adapted material is shared. It does not trigger when unchanged material merely appears beside other separate works in a collection. A collection keeps separate works separate, each retaining its own license. Combining two files into a single image creates adapted material under 4.0. Synchronising music with a moving image is expressly adapted material. Translation of text is normally an adaptation. Cropping, excerpting, editing and combining can each create an adaptation under applicable copyright law; do not declare a universal boundary. If your combination creates adapted material and one of the inputs uses SA, license the result under the SA-compatible license named by that input. If the inputs carry incompatible SA versions, you cannot legally share the combination.

On a Wikimedia Commons file page, the attribution field appears below the "Credit" line. The platform shows the author's username or real name, the source URL, and the license badge. If the uploader supplied additional attribution parties, those appear in the file's licensing section. The platform's terms require that all uploads be free of DRM and exclusive sublicensing terms. Version 4.0 expressly states that a recipient may not impose additional legal terms or effective technological measures that restrict another recipient's exercise of the licensed rights. A file that carries a CC badge but is hosted on a platform with download restrictions or exclusive terms creates a conflict. The CC badge does not resolve that conflict. The platform's own terms govern how you access the file, while the CC license governs what you may do with it once you have lawful access.

The single thing that most often goes wrong is assuming that because a file carries a Creative Commons badge, you are free to use it without checking the exact license version, the attribution parties, and whether the uploader actually owned the rights. Possession of a CC-licensed copy is not a guarantee that the uploader owned all necessary rights or that every component is covered. If the file contains a person's likeness, a trademark, or data from a database with separate rights, the CC license does not license those. Privacy, publicity, trademark, patent, contract and cultural-heritage law operate separately. The license applies only where copyright or similar rights require permission. Exceptions and limitations such as fair use or fair dealing operate separately; if an exception authorises the use, the license's conditions do not apply to that use, but their scope varies by jurisdiction. Never assume a CC badge resolves every legal question.