Q. What is the public domain?
Works that are no longer protected by copyright are within the public domain and can be used without permission or reimbursement. This is a result of either the work aging out of copyright protection or because an author chose to place their works in the public domain, foregoing copyright protection.
The length of copyright changed greatly during the 20th century, so it can be tricky to identify if a work is within the public domain or not. Anything published before 1923 is within the public domain. For later works use this Digital Copyright Slider to help determine the copyright status of a work.