There are fixed limits to how long copyright lasts. As of 2021, works published before 1925 are in the public domain, which means they can be reproduced without seeking or obtaining permission. Other works may be in the public domain because their copyright was not renewed (a requirement for works published before 1978) or because creators wish their works to be freely available. See the Stanford Libraries page on public domain issues for more information.
The Public Domain Review highlights and explores historical, literary, and artistic works that are now in the public domain.
Claiming fair use allows authors to build on the works of others in order to create new knowledge. Fair use is an analysis used when something is in copyright. That said, fair use claims can be tricky as every case is unique. There are four factors in the US copyright law (17 U.S.C. § 107) that authors are asked to consider:
1. Purpose and character of use: fair use is more likely to be allowed if work is primarily educational or commercial and the use is transformative—it adds value, such as critique or analysis, in some way
2. Nature of copyrighted work: if the work is factual and not creative, or published vs unpublished, the more likely a fair use claim will hold up; the more creative work the more likely it is to be covered by copyright.
3. Amount and substance used relative to the whole: use as much as needed but only what is necessary; everything used should be analyzed and incorporated into argument
4. Effect of use on potential market of work: this protects the rights of author or artist and their ability to make money from work—if an entire work is claimed as fair use, there is a greater risk of copyright infringement because the potential impact on sales for the artist is higher
The University of Minnesota provides a helpful tool for evaluating whether your use of a given work constitutes Fair Use. This tool is not a substitute for legal advice.
Additional Resource: