Prior Art

In order to get a patent on an invention, first and foremost your invention has to be new.  How can you tell if the invention is new or not? By looking to see if someone else has already come up with the same invention first. This is called searching for prior art.


If the patent examiner finds prior art and thinks it describes something too similar to the invention, then that’s evidence that the invention isn’t new anymore, so the examiner may reject the application.

Prior art is anything that the public already knows and is similar to the invention, and thus might be relevant to the patent application. For example, prior art can be other patents, newspaper articles, research papers, products in a store, blog posts, online videos— as long as it’s public and came before the patent application. Even past patent applications that got rejected count as prior art![1]

Officially, prior art must be:

  1. Public information

  2. Officially time-stamped

  3. Published a year or more before the patent application is submitted


The prior art has to be publicly published, so that others like the patent examiner can find it. It has to be officially time-stamped, in other words have an official publication date, to prove that it came first before the submitted patent application.  

Finally, in the US, the prior art must be published a year or more before the application gets submitted because there’s a one-year window for inventors to publish their work and still be able to patent it.  That is, if you publish your work and wait a year or more before filing for a patent, then you will not get the patent because your own work becomes prior art to your patent application!  

This is part of the “first to file” system in the US, where if two people come up with the same invention within a year of each other and both apply for a patent application, the first person to file for the patent would get it regardless of who did the work first during that year.


A neat trick for getting an official publication date, if you are publishing work online, is to submit your webpage to the Wayback Machine.[2] The website works by creating a copy of your webpage with an official time-stamp that is validated by the Internet Archive. Archiving your webpage on the Wayback Machine also helps make a permanent copy of your webpage. Since normal websites can change, a regular URL alone is not enough to be prior art.

Having your webpage archived is so useful because 1) you get an official publication date and 2) the archived website information wont change so the patent office trusts it as a reliable source. Even if your own website goes down, the archived version will still be available at!

If you don’t want someone else to patent your work, you have a few options.  You may choose to (1) keep it secret so nobody else knows about it.  Unfortunately, then nobody will be able to use the invention either!  You can also (2) get a patent on it, if you can afford the time and money required for the patent process.  Or you can (3) publish your work as widely as possible by blogging, publishing research papers, making and sharing the invention on social media, or even starting a business around your invention.  This way people can benefit from your invention and at the same time, you’re creating more prior art, which makes it harder for others to claim your work.

The last option is called defensive publication because the more prior art there is of your work, the easier it is to prove that your invention came first, preventing others from patenting it.

There is, however, something that complicates things...

Patent examiners mostly only look at other patents!

Even though prior art officially comes in many forms, patent examiners pretty much only look at existing patent and patent applications for prior art.  So even though other media like blog posts and research papers totally count legally as prior art, unfortunately examiners often miss them in their search.  How can this be?

It’s because practically patent examiners don’t have enough resources to find every single piece of prior art that exists in the universe.  


They have so many patent applications coming their way that they only get a total of about 19 hours to review an entire patent. This includes about 45 minutes to do a prior art search for each application and report on their findings.[3] The prior art that they do find must also be specific enough to legally invalidate the patent application, because patent examiners also have to write a public report explaining why they rejected the patent.

As a result, examiners usually only look at existing patents and patent applications, which are written in very specific legal language, to speed up their search and reporting.  They typically use the internal USPTO patent archive and google patents. So if your work isn’t in a patent or patent application, it also won’t be in one of these patent databases and likely will not get discovered by the examiner.  

In this case, even if the prior art exists, the patent can still get approved if the patent examiner doesn’t see it.


How you can help

Luckily there’s something you can do about it!  You can submit prior art directly to a patent application, or share your work in prior art archives that are known to be searched by patent examiners.   The USPTO recognizes the challenges of finding prior art, so they’re reaching out to the public to help.

If you know of prior art for a patent application, you can go directly to the patent application on the USPTO website and submit up to 3 pieces of prior art for free per patent.  Make it count, though, since you only get 3 free submissions per patent application! After that it’s $180.00 for up to 10 pieces of prior art.

Anybody can do this and you don’t need a lawyer. That said, you must be careful to file with properly formatted comments or else your submission will be thrown out by the USPTO. [4]


Even if there isn’t already a patent application for your work, you can still submit your work as prior art directly to the USPTO though the Prior Art Archive. [5] Created with support from the USPTO, this new archive is open to many more types of work—not just patents—and will be searched by patent examiners. The submissions are all free and you don’t need a lawyer for this either.

What if it’s too late? The patent already issued.

The patent examiner missed the prior art so patent issues anyway.  Now what? Turns out it’s not too late for prior art to save the day.

One option is to invalidate the patent by filing for an “inter partes review” or an IPR for short.  During this review, the USPTO takes a granted patent and reviews it again, with new prior art. The main drawback of an IPR is that it’s incredibly expensive—averaging in the hundreds of thousands of dollars to do one.  That’s much more than getting the patent in the first place!

The cost is so high because it’s a more complicated process to invalidate a patent than it is to file for one. You will need the help of a lawyer to do this, which is where most of the money will go. On average, filing an IPR costs between $300,000 to $600,000.[6]

If you don’t have the resources to invalidate the patent, all hope is not lost.  You see, a patent only has real power if someone uses it to sue someone else for patent infringement (learn more from our post here). However, if someone tries to use the faulty patent for a lawsuit, then during the court case people can still bring up you prior art as evidence to invalidate the patent.  In this case, you just have to make sure sure your prior art is public and easy to find so that others will find it and know to use it to defend themselves against the patent.


Okay, so It’s not perfect—it sucks that there still could be someone out there who owns a patent on what is rightfully your work. But at least it means that you can keep on doing the work you like and sharing it with the world, rather than getting bogged down and spending a ton of time and money on legal battles.

Why it’s so helpful to share

Whether you decide to openly publish your inventions through blogs and other media, or to publish through the patent office by getting a patent on your work, you are creating prior art that prevents other people from claiming your work in their own a patent.  The more you publish, the more prior art you create.

Beyond this, though, the more you publish, the more you also share the inventions with the world, and the more people can benefit from your ideas (which, by the way, is the whole reason patents were invented!).


Authors: Jie Qi (Berkman Klein Center; MIT Media Lab), Carol Lin (Harvard Law School), Ben Virgin (Suffolk Law School)

Illustrator: May Qi (Brown University)