If you’ve encountered patents, chances are you’ve heard the term “prior art.”

It’s one of the most common reasons that patent applications are rejected by the patent office, which makes it one of the most challenging hurdles to clear in getting a patent granted. Prior art can be used to show that your invention is not “new” or “non-obvious” — and these are two of the most important requirements for patentability.

That’s why it’s important to understand what counts as relevant prior art, and how that can affect your patent application.

What’s the Definition of Prior Art?

Technically speaking, what is considered prior art under U.S. law is defined by federal statute 35 U.S.C. 102, as amended by the America Invents Act (AIA).

In simpler terms: Prior art is any evidence that your invention was already publicly known or available, in whole or in part, before the effective filing date of your patent application.

Nevertheless, that’s still a fairly broad concept. To better pin down what prior art is (and isn’t!), let’s take a deep dive into several specific examples.

What Counts as Prior Art?

Many people make the mistake of assuming that prior art is limited to either existing products or issued patents. In other words, they believe (wrongly) that they’re entitled to a patent for an invention simply because that invention hasn’t been patented or implemented in a product yet.

But the range of information that counts as prior art is much broader than issued patents and commercial products. Generally speaking, prior art arises when someone has either made an idea available to the public, or filed a patent application that was eventually published or issued as a patent.

To list some common examples, prior art can include the following:

  1. A product that was available for sale
  2. Commercial use of the invention
  3. Articles, publications, or journals (printed or electronic)
  4. Presentation at a public event (a trade show, conference, etc.)
  5. Public knowledge or use of the invention (e.g. demonstration)
  6. A previously filed patent application (assuming the previous application eventually becomes a published application or an issued patent)

What examples 1-5 have in common: They were publicly available or publicly disclosed. It doesn’t matter whether the information is broadly accessible on the internet — factors like target audience, language, number of copies made, and geographic location are irrelevant for publications. To use an unlikely example, a high school textbook published only in Kazakhstan could still count as prior art.

Additionally, the information must have been publicly disclosed or publicly available before the effective filing date of your patent application. If your effective filing date is Sept. 1, 2023, then a magazine article published on Aug. 31, 2023, counts as prior art — as does an expired patent from 1950. However, provided you filed on Sept. 1, a demonstration of your product in October 2023 won’t qualify as prior art.

Example 6 above is slightly different from the other examples though, because a previously filed patent application might not be publicly available or publicly disclosed at the time you file your patent application. Patent applications typically remain secret for months or even years before they become public (as a published application or an issued patent).

But a previously filed patent application can qualify as prior art even if it becomes public only after your application is filed. So for example, if your effective filing date is Sept. 1, 2023, another patent application that was filed on Aug. 31, 2023 counts as prior art — even if it’s not published for several years.

What Doesn’t Count as Prior Art?

Information that becomes publicly disclosed or publicly available only after your application’s filing date generally doesn’t qualify as prior art. Similarly, patent applications filed after yours generally don’t qualify as prior art.

Here are four other notable exceptions to the examples provided above.


For a publication to be used to reject your claims for lacking novelty, it must disclose the invention with sufficient detail — that is, it must offer an “enabling disclosure.” Put another way, if someone with ordinary skill in the relevant field of technology cannot figure out how to make and use the invention from the prior disclosure, then it can’t be used as the basis for a Section 102 rejection. 

Let’s say you figure out how to build Iron Man’s suit and want to patent it. The comic books and movies themselves can’t be used to show that your claims lack novelty, because although they explain what the suit does, they don’t provide enough information to enable the average skilled person to build the suit.  

Keep in mind though that non-enabling prior art can be used to show that your invention is obvious.


Under certain circumstances, abandoned patent applications may remain confidential, disqualifying them as prior art. For one, provisional patent applications that aren’t converted to non-provisional applications are never published.

By default, non-provisional applications are published 18 months from filing. However, an application will not be published if the applicant abandons it more than four weeks before it’s due to be published.

Alternatively, if the application was filed only in the United States, the applicant can request non-publication — in which case the application will not be published unless and until a patent is granted.


As trade secrets are confidential by nature, they cannot be used as evidence of prior art. So another company’s trade secret invention typically couldn’t be used as prior art against your patent application, even if the other company developed their trade secret before you independently developed the same invention.


Even though it’s not advisable, in reality technology companies often need to disclose their work to third parties before they file a patent application — reasons to do this include gauging market interest, pursuing funding opportunities, and developing collaborations with other groups.

When information is shared with third parties under an obligation of confidentiality, the disclosure doesn’t count as prior art against your patent application. The best way to ensure that a disclosure will be considered confidential to have all parties sign a non-disclosure agreement (NDA).

What Happens if I Discover Prior Art?

There’s always going to be prior art for any invention. In the words attributed to a famous federal judge, “Only God works from nothing. Man must work with old elements.” Patentability doesn’t hinge on the existence of prior art. Instead, whether your invention is patentable depends on how different your invention is from the prior art.

There are two criteria for patentability over prior art. First, the invention must be new (or “novel” in the words of the statute) — which generally means it can’t be identical to any single product or reference. Quite simply, this prevents you from patenting ideas that already exist in the public sphere or in previously filed patent applications.

But at the next level, your invention needs to be inventive (or  “non-obvious in the words of the statute) — that is, more than a trivial variation of prior art. That means an invention typically can’t be patented if a person of ordinary skill in the relevant field of technology could derive the invention from the prior art by making obvious changes or substitutions.

It’s also important to inform the patent office if you know of any prior art that’s material to the patentability of the invention claimed in your patent application. Specifically, all inventors (and anyone substantively involved with a patent application) have a duty of disclosure, candor, and good faith in dealing with the patent office. Complying with this obligation is often easy, as the patent office provides a specific procedure for telling them about any relevant prior art.

How Can I Avoid Unexpected Prior Art?

In many cases, determining whether something qualifies as prior art and whether your invention is patentable over prior art can require relatively complex legal analysis. If you’re looking to move forward with a patent application, consider engaging a patent attorney who’s familiar with your industry. A skilled attorney will be able to tell you the options for dealing with known prior art for your specific circumstance.

But there’s always a possibility that you’ll encounter unexpected prior art — or even accidentally create prior art against yourself! Learn more in our blog, “How to Do a Prior Art Search Yourself” and download our FREE eBook, “Prior Art and the Patent Process” that discusses smart strategies you can employ to minimize those risks.

Get our free eBook to learn smart strategies for navigating prior art obstacles during the patent process.



But what should you do if you discover prior art against your invention? Download our FREE eBook to find out. Learn the following:

  • How does the industry define prior art?
  • How can you do an effective prior art search — and can you do it yourself?
  • How will discovering prior art affect the claims in your patent application?
  • What steps can you take to avoid unexpected prior art?
  • How can you avoid accidentally creating prior art against your own patents and applications?

Walk away equipped with smart strategies to navigate common prior art obstacles during the patent process.

Fill out the short form on this page to download this eBook today!


Michael K. Henry, Ph.D.

Michael K. Henry, Ph.D., is a principal and the firm’s founding member. He specializes in creating comprehensive, growth-oriented IP strategies for early-stage tech companies.