|This page documents a Wikipedia policy with legal considerations.|
|This page in a nutshell: Do not add content to Wikipedia if you think that doing so may be a copyright violation. Contributors should take steps to remove any copyright violations that they find.|
|For more information on copy and pasting text, see Wikipedia:Copying text from other sources. For more information on closely paraphrasing text, see Wikipedia:Close paraphrasing.|
One of the most important aspects of Wikipedia is that its text (not media, but that will be discussed shortly) may be freely redistributed, reused and built upon by anyone, under the terms of the Creative Commons Attribution-ShareAlike 3.0 Unported License (CC BY-SA) and, except where otherwise noted, the GNU Free Documentation License (GFDL) (unversioned, with no invariant sections, front-cover texts, or back-cover texts). Contributors agree to release their original content under both licenses when they submit it, and material from public domain sources or other compatibly licensed sources may also be used in accordance with the copyright policy, provided correct attribution is given.
However, copying material without the permission of the copyright holder from sources that are not public domain or compatibly licensed (unless it's a brief quotation used in accordance with Wikipedia's non-free content policy and guideline) is likely to be a copyright violation. Even inserting text copied with some changes can be a copyright violation if there is substantial linguistic similarity in creative language or sentence structure; this is known as close paraphrasing, which can also raise concerns about plagiarism. Such situations should be treated seriously, as copyright violations not only harm Wikipedia's redistributability, but also create legal issues.
The situation for images and other media is slightly different, as a wider variety of licenses is accepted. But, in short, media which is not available under a suitable free license and which does not meet the non-free content criteria, should be assumed to be unacceptable. See Wikipedia:Image use policy and Wikipedia:Non-free content for details of this and Wikipedia:Guide to image deletion for some suggested steps for handling problems with images or other files.
Copyright infringing material should also not be linked to.