What is meant by the term Public Domain? According to Plagiarism.org, "the term Public Domain has a very specific meaning. In short, it is used to denote works that have no copyright protection, meaning that they can be used freely without permission from the creator or another rightsholder ... most content on the Internet is NOT public domain ... Whether a work is in the public domain deals only with its copyright status. That determines whether you can copy and distribute the work. It says nothing about your ethical obligations to cite and attribute it ... even if the content you're using is actually in the public domain, you still need to cite. The rules of plagiarism and citation apply just as much to works in the public domain as they do [to] works still under copyright" (Turnitin, LLC, 2018).
Public Domain Day was January 1, 2019. As of that day, works from 1923 have been made free fo all to use and build upon, without permission or fee.