Public Domain films are films that are either no longer protected by copyright, meaning they were licensed by copyright and aged out of protection, or they had their copyright protection either waived by the creator or not renewed.
As of January 1, 2024, all films from 1928 or earlier are considered within the public domain in the United States.
Although there are plenty of legitimate public domain films, which can be accessed for free online, some films are illegally downloaded and uploaded to the internet with the incorrect public domain label. Be careful that the film you are accessing, copying, distributing, or showing actually falls within public domain and fair use. Remember, it is always the obligation of the researcher to determine any restrictions on use.