Prior art is earlier information, technology, publications, patents, products, or public knowledge that may affect whether an invention can be patented.
In plain language, it is what was already known or disclosed before the claimed invention. Patent examiners, applicants, and challengers use prior art to evaluate novelty and non-obviousness.
Why it matters
Prior art matters because patents are not granted for ideas that are already known or obvious in light of earlier disclosures. A strong prior-art reference can narrow patent claims, block an application, or help invalidate an issued patent.
The term is central to patent searching, patent prosecution, licensing, and litigation.
Where it appears
Prior art appears in patent applications, office actions, invalidity arguments, patent searches, expert reports, licensing due diligence, and patent-infringement lawsuits.
Practical example
An inventor claims a new mechanical feature, but an older patent shows the same feature in nearly identical form. That older patent may be prior art against the new application.
How it differs from nearby terms
Prior art differs from a patent. A patent is a granted legal right; prior art is earlier information used to evaluate whether a claimed invention deserves or can keep that right.
It also differs from a patent claim, which defines the legal boundaries of the invention in a patent.
Related terms
Quick knowledge check
Question: What is prior art used to evaluate?
Answer: It is used to evaluate patentability or validity by showing what was already known or disclosed.