Materials in the public domain are items that are not protected under copyright, trademark, or patent laws. This means that you can use public domain materials for any purpose without requesting permission from a copyright holder.

Items typically enter the public domain either because the copyright holder relinquishes rights or because copyright protections have expired. Additionally, some materials - like federal publications - automatically go into the public domain because of the nature of the work.

Although terms have changed over time, currently copyright protections are in place for the life of the author plus 70 years. Once this time has elapsed, materials then enter the public domain for general use.

That said, it can be tricky determining if something is in the public domain--in no small part because copyright legislation has changed over time. In general, when you need to determine whether works fall into the public domain, consider the following:

• Works published in 1923 will become public domain in 2019. Works published in 1924 will join the public domain in 2020, and so on.
• Works dating from 1923-1963 are in the public domain if the author did not renew copyright claims with the Copyright Office. 
• Works published 1923-1977 are in the public domain if they do not feature a copyright notice.
• If the author specifically noted that a work is "dedicated to the public domain," then the work is in the public domain.
• Facts and ideas cannot be copyrighted and so can be freely reused.
• Materials published by the U.S. government are in the public domain. However, state publications may or may not be in the public domain depending on local legislation.

Infographic used with permission of GFCLearnFree.org.