Creative Commons is a nonprofit organization that provides free copyright licenses to enable sharing and use of creative works. The licenses allow creators to modify their default "all rights reserved" copyright to "some rights reserved" based on their needs. The licenses include Attribution, Attribution-ShareAlike, Attribution-NonCommercial, and others that vary in what uses are allowed and if derivatives must be shared under the same terms. Fair use is a limitation on copyright that allows limited use of copyrighted works for purposes like commentary or research without permission. When determining if a use is fair, courts consider the purpose, nature of the work, amount used, and effect on the work's potential market.