Wikipedia:File copyright tags/Free licenses
Free content is free as in freedom. This page links to some of the most popular licenses for releasing such content. This page can be reached via when forwarding the full URL is not convenient. If an image is available under one of these licenses, it is acceptable to be used in Wikipedia.
Generally, a work licensed under a CC tag with more requirements cannot be integrated into a work licensed under a more permissive CC license (such as integrating a CC-BY-SA work into a CC-BY work), unless the entire target work switches to the less permissive license.
Other Creative Commons licenses exist but are non-free for use in Wikipedia. See Non-free Creative Commons licenses for a full list and explanation.
Note: The licenses in this section require reprinting the entire license text with any reuse of the image. If you created the image yourself, please consider using a different license. If one includes any of the content, the entire book/section goes under GFDL, unlike CC-BY-SA.