Public domain resources are resources that are not subject to copyright, either because the copyright has expired or because their creators have assigned them to the public domain. Public domain works can be freely copied without requesting permission from the owner of the copyright.

In general, resources might fall into the public domain if they are: 

• Published before 1929, or between 1929 and 1978 without a copyright notice, renewal, or registration.
• Published after 1978 or between 1929 and 1978 if the copyright was renewed: 70 years after the creator has died.
• Published by a corporation (e.g. Disney), 95 years after publication or 120 after creation, whichever is shorter.
• Published under a Creative Commons CC0 indicator.
• US government publications. 
• Scientific and mathematical formulae, theorems, and laws of nature.
• Laws, regulations, judicial opinions, and legislative reports.

Due to various copyright law exceptions and global differences, this is not a complete list, nor is it legal advice. For more information, visit Copyright.gov and read through their Circular 22 publication.

Keep in mind that even if a public domain source is not subject to copyright, you still need to cite it! You can find out more on the Copyright and Fair Use page and our Citing Sources guide.