Searching for Patents and Prior Art

By Elliot Stein, A.B. and Mark Maloney, JD, MS

Executing a thorough prior art search can be a daunting and time-consuming affair, but it is a crucial part of the academic entrepreneur's workflow because it can reveal whether or not a solution is truly novel. Increasing the comprehensiveness of a prior art search increases the likelihood of success for a new patent because the inventor becomes more aware of the state of the field, can better create distinctions between his or her invention and existing inventions, and is able to preempt sources of conflict with prior patent literature.

"Prior art" refers to any publicly available description, reference, or physical manifestation of an invention. In addition to doing a patent search, it is imperative to thoroughly search the prior art surrounding an invention since the invention may have been previously described in books, publications, broadcasts, artwork, literature on the internet etc., even if this mention has not resulted in the creation of an official patent or patent application.

Patents are a specific subset of prior art. The United States Patent and Trademark Office (USPTO) issues and renews patents and oversees the maintenance of the US patent database, including all patent applications that have been published but not issued. According to the USPTO , a patent may be issued to “[...] anyone who invents or discovers any new and useful process, machine, article of manufacture, or composition of matter, or any new and useful improvement thereof” (USPTO). Importantly, patentable inventions must be novel and non-obvious.

Many search tools exist to facilitate a search of current patents and other prior art. The remainder of this post will enumerate a method of patent searching:

  1. Document: The most important step of any patent and prior art review is that the searcher records thorough documentation of the patent and prior art searches. This documentation may prove essential in later discussions with a patent lawyer or when filling patent paperwork to demonstrate that a reasonably extensive search was performed.

  2. Think: what are the best terms to describe a new invention? What are the synonyms? Are there any terms of art? Research and document the key terms for a proposed invention

  3. Find CPCs: The USPTO uses a unique Dewey-Decimal-System-like classification system called “Cooperative Patent Classification” (CPC). Finding the CPC codes that most precisely approximate a new invention will facilitate searching the current patent literature and reduce time wasted with irrelevant patents. Here’s where to start: navigate to, find the general search box in the upper right corner and type “CPC scheme [enter search term(s)]”. The list revealed by the search will display potential CPC codes that closely approximate the category of the new invention. The search terms may need to be altered in order to find the best CPC. Write down any relevant CPC codes and try to find the one that most specifically resembles the invention. If there is a CPC definition available for a CPC code, review it to ensure that it is applicable for the present invention and not so specific that it would exclude your invention.

  4. Review patents: Navigate back to and click quick links in the upper right. Choose “PaFT”, and on the next screen, write the CPC code that best approximated the category containing the new invention found in step 3. Be sure to remove the space in between the first and second part of the code. In the field to the write of the entry box, select “Current CPC Classification” from the dropdown. Press search. The next screen will display a listing of all the patents matching that CPC code. Read each patent thoroughly, making notes as needed. Repeat this step for each of the relevant CPC codes found in step 3.

  5. Review patent applications: Navigate back to one last time. Click quick links in the upper right. Choose “AppFT”, and on the next screen, do identical searches as in step 4. This time, the results will be published patent applications, not issued patents as in step 4. While these results are not issued patents, they are still considered prior art and must be treated as such. Again, take care to document your search terms and the results.

  6. Alternate searching strategies: note that it is possible to search for prior art and patents using platforms independent from the USPTO. For instance, offers a powerful tool for searching both patents and prior art (courtesy of Google Scholar) in one search. Google will also automatically determine the most relevant CPC codes for search terms, but it is advisable to do a thorough CPC analysis as described in step 3 before searching on Google Patents so that nothing is missed.  

  7. Expanding the search: next steps may include searching the European Patent Office (EPO), Japan Patent Office (JPO), etc. in order to make the search international. In addition, it is appropriate to search for prior art at this point in the process. Google Scholar, Web, and Book search may prove helpful, but not exhaustive, in this regard.

This step-by-step guide relies heavily upon the information located at A more detailed introduction (video) to navigating the USPTO’s search tools and doing a patent search may be found at

Elliot Stein, A.B. is a Candidate for Doctor of Medicine & Master of Science in Translational Research at the Perelman School of Medicine at the University of Pennsylvania |
Mark Maloney, JD, MS is the Associate Director and IP Manager, Technology Licensing at Johns Hopkins Technology Ventures  |

Back to the homepage

Photo by Glenn Carstens-Peters on Unsplash