Can nonpreferred embodiments in a patent be used 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.

Yes, nonpreferred embodiments in a patent can be used as prior art. According to MPEP 2123:

“A reference may be relied upon for all that it would have reasonably suggested to one having ordinary skill in the art, including nonpreferred embodiments.”

This means that even if a patent describes certain embodiments as less desirable, they can still be used as prior art. The MPEP further clarifies:

“Disclosed examples and preferred embodiments do not constitute a teaching away from a broader disclosure or nonpreferred embodiments.”

This principle ensures that all relevant prior art is considered during patent examination, not just the preferred or optimal solutions described in a reference.