The public domain is the collection of all expressive works for which no one owns the copyright - or to look at it another way, the collection of works which everyone owns! It is a wellspring of knowledge, culture, and creative growth. Expansion of the public domain is, by some accounts, the whole reason we have copyright in the first place!
A work is in the public domain if its term of copyright protection is over, or if it never met the requirements for copyright protection in the first place. Here's a couple examples:
- Copyright is over
In the U.S., the only sure-bet works where copyright has ended are those that were published in the U.S. before 1923. Many works that were published in other countries prior to 1923 are still covered by copyright in the U.S. And it's worth noting that it is entirely possible for a work to be in the public domain in one country, and still covered by copyright in another!
Nevertheless, copyright has also ended for many works that were published more recently - even as late as the 1960s and 1970s - see the resources below for more information on all the details!
- Copyright never existed
All works created by the U.S. federal government (and federal employees in the course of their work) are in the public domain in the U.S. from the moment of their creation - there is no copyright, in the U.S., in U.S. federal government works.
Works in the public domain may be used freely by anyone, for any purpose, without copyright permission from anyone - because no one owns exclusive rights in these works. However, use of public domain works can still raise issues around defamation, rights of publicity, trademark, and related rights of individuals or entities portrayed in the materials.Public Domain Information Resources:
- The Copyright Slider - CC by-nc-sa Michael Brewer and ALA Office for Information Technology Policy A useful (and fun!) tool for looking up copyright term and public domain possibilities via date and various conditions of publication.
- The Durationator - from Tulane Law School's Usable Past project Another useful and fun tool; still in development.
- Copyright Term and the Public Domain in the United States - CC by Peter Hirtle, Cornell Copyright Information Center The most exhaustive resource available, an incredibly detailed chart of copyright term and public domain considerations and dates.
- Search Copyright Records at the U.S. Copyright Office
- Copyright Renewal Records (Michael Lesk; Rutgers University SCILS)
More basics: Copyright's Purpose: What Copyright is For | How Copyright Works: The Details | The Public Domain | Exceptions & Limitations: Classroom Use, Fair Use, and more