What is the Public Domain?
The Merriam-Webster Dictionary (2017) defines public domain as “the realm embracing property rights that belong to the community at large, are unprotected by copyright or patent, and are subject to appropriation by anyone.” Creative works published in the United States (U.S.) before 1923, documents produced by the U.S. federal government, and publications from U.S. state governments are the most common materials in the public domain. For information on what types of works receive copyright protection, please visit the Copyright Basics page.
For example, this painting is in the public domain:
The Japanese Footbridge, Claude Monet, 1899
Creative works can also be dedicated to the public domain using the CC0 (CC Zero) tool from Creative Commons. For more information about CC0 and the public domain, please visit the Creative Commons Public Domain website.
Content in the public domain can also include some oddball or uncommon creations. These creations include objects created by nature, plants, animals, machines, random selection, or any objects not created by a human. For example, a flower pressed in a book might create a unique outline on the page, but that outline will not receive copyright; it was created by the flower and the book, and, by law, only human beings can own copyrights. Another interesting example involves a lawsuit concerning selfies taken by a monkey; because the monkey, and not a human, took the photos, the U.S. Copyright Office has stated that a "photograph taken by a monkey" is not an item that can be copyrighted. Therefore, many contend that the photos are in the public domain, such as this photo:
Macaque Self-Portrait, Indonesian island of Sulawesi, 2011
Even though creative works may no longer be protected by copyright or patent law, the creative works may still have other types of protections. These protections can include trademark, publicity, privacy, HIPPA, and FERPA. If the work is still protected through one of these areas, then the content may technically be in the public domain but be afforded other protections that do not allow it to act as if it was in the public domain. For example, suppose you want to publish some letters that were written many years ago, and you've determined that the letters are no longer protected by copyright; however, you discover that the letters reveal private information about individuals who are still alive today, and therefore, you would have to seek permission from those individuals before you decide to publish the letters.
CC0 (CC Zero)
Public Domain Mark (PDM)
Once you have these answers, use the linked resources below to determine if the work is in the public domain:
As you might have noticed, attribution (i.e. citation/credit) is given to the artist of the Monet painting at the top of the page. While U.S. law does not require attribution to the creators of public domain works, it is considered ethical and moral to provide that information about creators/artists/authors.
Having said that, works that are in the public domain can generally be used freely, without permissions, so you can do just about anything with them! Well, maybe not anything. Keep in mind that just because a work is within the public domain, you can't take someone's painting hanging on the wall at home or in a museum. But legally obtained copies of a public domain work no longer have copyright protection, meaning you are free to use the works in the same way copyright holders use their own works. There's no need to seek permission or rely on an exemption in the law.
So what can you do with a creative work in the public domain? Here are some examples of the exclusive rights of copyright holders that you now have the freedom to exercise:
Create derivative works
Derivative works are works that are based in whole or in part on the original work (e.g. a sequel or movie adaptation of a book), you can feel free to remix, rearrange, translate, adapt, and alter the original work to your preferences. Here is a great example of a derivative work based on a public domain work (the Mona Lisa):
Title: Mona Lisa
In addition, Duchamp's derivative work is also in the public domain, so anyone could alter his derivative work, perhaps by lengthening the moustache or adding hair on the chest! (Note, however, that the work is still under copyright in its home country of France until 2039.)
Reproduce the work in whole or in part
For example, you could take the play Hamlet and make your own PDF copies of it, put annotations in it, make a cover for it, and distribute it or sell it online for others to read.
Publicly perform or display the work
An example of publicly performing the work would be performing a play in front of an audience, and an example of displaying a work would be posting a photo on an online blog. Another example would be uploading a film online for others to view, such as on YouTube.
Note: with films and other audiovisual works, you have to be careful, because there are layers of potentially copyrighted material in the film, such as the music/soundtrack, literature, characters, art, etc.
Donna Reed and James Stewart, It's a Wonderful Life, 1946