How does experimental use affect public use in patent law?

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.

Experimental use can negate what would otherwise be considered a public use in patent law. The MPEP 2133.03(e) states:

“The use of an invention by the inventor himself, or of any other person under his direction, by way of experiment, and in order to bring the invention to perfection, has never been regarded as [a public] use.”

This means that if an inventor is testing their invention to improve or perfect it, even if done in public, it may not count as a public use that would bar patentability. However, the experimental use must be the primary purpose of the activity.