When the copyright expires for a work, it enters the public domain, meaning anyone can freely use it without seeking permission or paying a fee. Currently, the public domain cutoff date is 1923. That cutoff year will begin moving forward on January 1, 2019, but as of this writing, works published prior to 1923 are in the public domain in the United States . However, international laws can complicate public domain research. The best rule of thumb is, "When in Rome, do as the Romans do." In the U.S., follow U.S. Copyright Laws. In the UK, follow UK Copyright Laws.
For example, since Anne Frank died in 1945 (seventy years ago), the Diary of Anne Frank recently entered the public domain in Europe along with all countries with Life + 70 copyright duration. However, under U.S. Copyright Law, the diary is still protected since U.S. copyright duration for works published between 1923 and 1978 is 95 years after the date of publication. This means the diary won't enter the public domain in the U.S. until 2042 (1947 + 95). Conversely, some works can be in the public domain in the U.S. but not in the work's country of origin. For example, some works by Finnish composer Jean Sibelius are in the public domain in the U.S. but not in his home country. Sibelius did not die until 1957, thus extending the copyright of his works in Europe to 2027. However, because some of his early works were published prior to 1923, they are in the public domain in the United States. One such example is the famous tone poem Finlandia, composed in 1899 and published soon after, which contains the tune for the well-beloved hymn "Be Still My Soul."
As you can see, determining public domain status can be quite complicated. See below for additional resources to assist in your research.
Copyright Term and the Public Domain in the United States is the most widely used and referenced chart in determining if a work is in the public domain. Created by Peter Hirtle, Cornell University Libraries.
List of Countries’ Copyright Lengths – List of countries and their copyright terms-the lengths in years. When a work’s copyright term ends–when the work passes into the public domain.
Public Domain Slider Tool is a helpful digital tool for determining public domain status of a work. Published by the American Library Association.
Copyright Renewal Database (Books only) - A searchable database of the copyright renewal records received by the U.S. Copyright Office from 1950 to 1992 and for books published in the U.S. from 1923 to 1963.
Catalog of Copyright Entries/Renewals (All works) - Digitized Copyright Office records for works published between 1923 and 1978.
Online U.S. Copyright Catalog (1978 to present) - Online database of all registered copyrighted works in the U.S. after 1978.
Copyright Research, Stanford Universities Libraries
Researching the Copyright Status of a Book: Protected or Public Domain? Kenneth D. Crews, Columbia University