When is a patent considered available to the public for prior art purposes?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

A patent is considered available to the public for prior art purposes under 35 U.S.C. 102(a) or pre-AIA 35 U.S.C. 102(a) or (b) when it is made sufficiently accessible. According to MPEP 2126:

“The patent is sufficiently available to the public for the purposes of 35 U.S.C. 102(a) or pre-AIA 35 U.S.C. 102(a) or (b) if it is laid open for public inspection or disseminated in printed form.”

The date that the patent becomes available to the public is the date it can be used as a reference under these sections. This principle was upheld in In re Ekenstam, where the court determined that the critical date is when the patent becomes publicly accessible.