Your original works fixed in any tangible medium of expression are protected by copyright law, which is a form of intellectual property (IP) law. Once secured, your IP rights may be licensed, transferred, or devised. Learn about copyright basics from the US Copyright Office.
Making sure that your usage of others’ copyrighted work does not infringe upon their legal rights can be a daunting process. First, you need to determine whether the work you intend to use is copyrighted (See How to investigate the copyright status of a work). Second, if the work is copyrighted, do you need to get permission and how to get such permission? No permission is needed if your intended use falls under one of the copyright exceptions including the fair use doctrine.