Copyright is a form of legal protection automatically provided to creative works such as books, music, or art.
Copyright law is intended to encourage people to create new works. By limiting how others can use a newly-created work for some period of time, copyright law gives creators more control over the use of their works and increases their potential for compensation.
According to the law, only the person who controls the copyright (originally the creator) is allowed to:
The creator of a copyrighted work can give others permission to do these things with the work and can completely transfer these rights to someone else in a way that gives up these rights for themselves. For example, a book author will often transfer their copyrights to a publisher in exchange for money related to the sales of the book. After that transfer, authors can no longer give permission to anyone else to do these things and needs permission from the publisher to do these things themselves.
The creator, or person the creator transfers their rights to, is said to “control copyright” in the work and sometimes described as the copyright owner.
When someone other than the copyright owner uses the work in one of these protected ways without permission (or other justification under copyright law), it is called copyright infringement.
Some works that might qualify for copyright protection are instead part of the public domain. The public has the full rights to use these work without obtaining permission and no one can come to control those rights in the future.
There are three common ways that works enter the public domain:
Probably the most common category of public domain works is those for which copyright has expired. Identifying these works is complicated by the fact that the term of copyright has varied over time and for different types of work. One useful fact is that any works published in the U.S. before 1923 will be part of the public domain.
Before March 1, 1989, creators had to take proactive steps to arrange for their works to be protected by copyright. If they did not take those steps, the work entered the public domain. Many works created from 1923 to 1989 are in the public domain, but more information than the publication date is needed in order to make that determination
Some copyright owners decide to place their work in the public domain. For example, any works created by the United States Government including: federal judicial decisions, federal statutes, speeches of federal government officials given in the course of their employment, federal government press releases, and federal government reports (such as census reports) are placed in the public domain and their use is not limited by copyrights. The practices of state and local governments vary widely and can change over time so must be investigated on a case-by-case basis.
Creative Commons (CC) licenses make it easier to share and re-use creative work including educational resources while complying with copyright law. They allow copyright owners to encourage others to use and sometimes remix their work without first asking permission. Works with a CC license allow re-use of the work under certain conditions depending on the license chosen by the copyright holder.
Below is an infographic describing the Creative Commons licenses.