The Wayback Machine is a digital archive maintained by the Internet Archive, a non-profit organization. It's used to view archived versions of websites as they existed at specific points in time. In patent law, the Wayback Machine can be a valuable tool for establishing the public accessibility of online content on a specific date. According to the MPEP: "Prior art obtained via the Wayback Machine sets forth a prima facie case that the art was publicly accessible at the date and time provided in the time stamp. The burden then shifts to the applicant should they wish to challenge the authenticity, reliability or accessibility of such information." This means that when an examiner cites a webpage archived by the Wayback Machine as prior art, it's presumed to have been publicly accessible on the date shown in the archive's timestamp. If an applicant wants to dispute this, they bear the burden of proving otherwise. The MPEP cites the case of Valve Corp. v. Ironburg Inventions Ltd. to support this use of the Wayback Machine in establishing public accessibility dates for prior art references. To learn more: Wayback Machine Internet Archive prior art public accessibility patent law