How are U.S. patent application publications considered as prior art?

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.

U.S. patent application publications are considered prior art under various sections of the patent law. According to MPEP 901.03:

“U.S. patent application publications are prior art under pre-AIA 35 U.S.C. 102(a) and 102(b) and 35 U.S.C. 102(a)(1) as of the publication date. Under pre-AIA 35 U.S.C. 102(e)(1) and 35 U.S.C. 102(a)(2), a U.S. patent application publication under 35 U.S.C. 122(b) is considered to be prior art as of the earliest effective U.S. filing date of the published application.”

This means that published patent applications can be used as prior art references from their publication date or, in some cases, from their earliest effective U.S. filing date, depending on the specific section of the law being applied.