The phrase "public domain" (PD) is commonly used to refer to works that are not protected by copyright law. Works in the public domain can be used freely, without obtaining permission from or compensating the copyright owner.
Works can enter the public domain in several ways:
- U.S. government documents. Note, if the work was produced by a consultant or freelancer to the government, the consultant/freelancer may have protection unless the copyright is transferred to the U.S. Federal government.
- Copyright term has expired. Cornell University Library developed a chart that summarizes copyright expiration dates in the United States. The American Library Association Office for Information Technology Policy has created an easy reference tool for deciding if a work is in the public domain. Requires Flash.
- The creator(s) failed to adhere to copyright requirements at the time of publication or renewal.
- Ideas, facts and discoveries. Examples include facts, short phrases, ideas.
- The copyright owner(s) has dedicated the work to the public domain. The Creative Commons Public Domain Dedication, CC0 (aka CC Zero) is a public dedication tool, which allows creators to give up their copyright and put their works into the worldwide public domain. CC0 allows reusers to distribute, remix, adapt, and build upon the material in any medium or format, with no conditions.
It is important not to confuse public availability with public domain. Before using the work, check if the work is in the public domain. The availability of a work online has nothing to do with its copyright status.
Additionally, it is recommended, as a best practice to cite public domain works. Not citing your sources could be considered plagiarism, which can have severe professional and educational consequences.
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