Good news! Not everything is protected by copyright. There are vast collections of content that have no restrictions on use. If something is in the public domain, you can copy it, publish it, remix it, etc., etc. Below are the main public domain categories.
U.S. federal government works. The federal government dedicates its content to the public domain. This includes works by agencies or government employees in the course of their duties.
Everything created before 1923. You can safely assume that anything published before 1923 is in the public domain. This include books, famous works of art, photographs, and even some early motion pictures.
A lot of things created between 1923 and 1989. Unfortunately, determining copyright for works published between 1923 and 1989 is difficult. See the box below, Determining Public Domain Status, for more information. You can assume works made since 1989 are copyrighted (with a few exceptions, like Creative Commons materials).
The table below, borrowed from Stanford's helpful and thorough fair use and copyright guide, provides general guidelines for when works are likely to enter the public domain.
|Works published in the US before 1923||In the public domain.|
|Works published in the US after 1923 but before 1964||Initial term of 28 years. If not renewed during the 28th year, the work falls into the public domain.|
|Generally, if a work was published after 1922 but before March 1, 1989||Generally, if a work was published without copyright notice under the authorization of the copyright owner and the law does not provide an exception for the omission, the work is in the public domain.|
For a more detailed version, see the Cornell Copyright Term chart, below.
How do you know if a work was published with notice or if copyright was renewed? Below are some resources to help you. It's not always easy or possible to determine this.