How to Do a Patent Search

By: Stephanie Crawford  | 
A patent gives you legal protection against infringement on your ideas and inventions. Before you can claim your own, however, you'll need to determine what's already been patented.
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Have you ever had an idea for some gadget to make life easier and wondered if it had been invented yet? Ever thought about selling your invention and needed to know if someone already beat you to it? One way to find these answers is to look for patents on similar gadgets and determine whether your invention is unique.

A patent is a legal document describing the unique details of an invention and granting one or more persons the right to prevent others from making or selling that invention [source: FreePatentsOnline, "Legal Definition"]. Others may still try to take credit for and profit from the invention, but the patent gives the grantee the option to take legal action against those who do. In the U.S., patents are approved and managed by the Patent and Trademark Office (USPTO), part of the Department of Commerce. For more on patents themselves, see our article How Patents Work.


To find out if someone has a patent on a particular idea or object, you'll need to do a patent search. However, this isn't as easy as entering a few keywords into a Web search engine. The USPTO patent database alone is massive, and an international search could be overwhelming. So, start by narrowing down what you're searching for and why.

First, identify the type of patent you're trying to find from the three types managed by the USPTO:

  • Utility patents are the most common type, covering objects that either function in some new way or produce some completely new result that similar objects hadn't been able to before.
  • Design patents encompass enhancements to an existing object that don't change its functionality.
  • Plant patents deal with new types of plants that are grown using grafts, cuttings or some other asexual method. However, genetically engineered plants fall under the umbrella of utility patents.

Next, choose your search approach based on the reason you're searching. If you're just checking for information, novelty or state-of-the-art searches are the best approaches. If you're looking to take legal action or defend yourself against it, an infringement or validity search is more appropriate.

This article will focus mainly on how the online patent searching process works in the United States, with nods to international systems and offline searches. First, let's find out how patents are classified in the U.S. so we know where to start looking.


How Patents Are Organized

In 2009 alone, the U.S. Patent and Trademark Office received nearly half a million patent applications and granted about 40 percent of them [source: USPTO, "Statistics"]. Each of these applications requires detailed text descriptions and drawings of the invention. When you do your patent search, this is the first documentation you'll find.

Each patent may also reference other patents and non-patent literature that describe the prior art closest to the invention. Prior art is technology related to the new invention that people had previously described in a publication (such as a science journal) or made, sold or used for the same purpose as the invention. For example, suppose you're inventing a new coffee grinder. Prior art would include existing coffee grinders that operate in a similar way but don't include your new improvements. Prior art could also be some newly discovered grinding process your invention is using that was recently published in an engineering magazine. Depending on what you're looking for, you might want to examine the referenced documents describing this prior art.


No matter what kind of patent search you undertake, knowing how all these documents are categorized can help you narrow your search. The agency uses its U.S. Patent Classification System (USPCS) to stay organized. The USPCS groups patents into classes that identify some major category of objects, including everything from apparel (class 002) to telecommunications (class 455). Each class includes subclasses, and each subclass can include other subclasses. This hierarchy might be several levels deep before it is precise enough to classify a particular patent, and the USPTO creates new subclasses as needed for even more precision [source: USPTO, "USPC"].

When reading the classification on the patent itself, you'll notice a class/subclass pair using a slash. For example, "2/456" means class two and subclass 456. For a complete list of all the current classifications in the USPCS, see the USPCS index at or the Manual of Classification (MOC) published by the USPTO. 

If your search takes you outside the U.S., you should be aware that international patent agencies use different classification systems. For example, countries in Europe use the International Patent Classification (IPC) and the European Classification (ECLA). Some examples of international patent organizations include the Japan Patent Office (JPO), the Korea Intellectual Property Rights Information Service (KIPRIS) and the State Intellectual Property Office (SIPO) of the People's Republic of China. U.S. patents that are also filed in other countries list the patent's international classifications, which saves you time in your search.


Challenges of a Patent Search

Sorting through massive patent databases can be a pain.
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In June 2010, Google and the United States ]Patent and Trademark Office announced a two-year agreement in which Google would make about 10 terabytes of bulk patent and trademark data available online for free. This partnership was part of a larger effort known as the Open Government Initiative, spearheaded by President Barack Obama.

The USPTO has been offering free patent data online for years, but some patent information wasn't accessible to the public or entailed large fees for processing bulk files. Now, thanks to the Google-USPTO partnership, huge amounts of patent data are available online through Google Patents at no cost -- and in a much more accessible format. Privately run Web sites, some of which have also provided free patent search tools for years, now have more resources to work with and have come up with even more innovative ways for users to search and retrieve patent data.


These new search options help address two of the biggest challenges of patent searching:

  • Filtering a large volume of data -- You can narrow down the search significantly if you're looking for a design or plant patent, but most searches are utility searches (the most common type) and involve sorting through massive amounts of data. Electronic records (text and drawings) go back to 1976, and electronic scans include patent documents going back to 1790 [source: USPTO, "Search"].
  • Reading patent documents -- Even after you narrow down the data with keywords and subclasses, you still have to wade through verbose descriptions in each patent you find. In addition, descriptions may be barely distinguishable between patents of similar objects.

Each patent search Web site has its own approach to searching and retrieving patent data and presenting the results to you. Google Patents uses the same search technology behind Google Book Search [source: Google Patents]. FreePatentsOnline has improved the search algorithms to find concepts, not just keywords, and it offers tutorials to educate the novice researcher about patents and patent searching. Some sites offer extra features, too, such as access to international patent data, an RSS feed of the latest patent applications and quick links to the latest patents in certain classifications [source:, "Home,", PatentStorm].

Even with all the features available in patent search engines, you'll still need time and expertise to meet patent search challenges and obtain comprehensive results. One option is to go to a public search facility such as the USPTO's Public Search Facility in Virginia. Or you could visit a special, regional patent library called a Patent and Trademark Depository Library (PTDL)  in your area. These special facilities offer a wealth of online and offline patent search resources and staff members who can teach you how to use them.

When you don't have time to conduct your own search or you're uncertain about your level of expertise, professional services can help.


Costs of a Patent Search

The U.S. Patent and Trademark Office receives more than a thousand patent applications a day.
Don Farrall/Photodisc/Getty Images

If you're serious about your patent search, you may not want to rely on the results from a free search engine, which are limited and might be more likely to result in legal action against you. A professional patent searcher, however, can help you keep that risk to a minimum. These professionals go beyond software-driven algorithms, applying their personal expertise to the search. Professional patent searches take about five business days, starting from the time they've received all the information they need from you for the search.

The cost of this professional service depends on what you're looking for and who's providing the service. For example, the U.S. Patent and Trademark Office charges for searches by the type of patent, while prices its services by the type of search you need. Depending on your search requirements, your costs could range from $100 to nearly $2,000 -- or higher.


Besides the fees for the search services, there may be an additional cost to request printed copies of the patent documents identified by the search [source: USPTO, "Fee"]. Also, if you're in a business that needs to make frequent searches of patent data, such as an R & D department developing products for a corporation, you might consider subscribing to sophisticated patent-searching tools and services rather than paying a separate fee for each new search [source: Delphion].

Even if you don't conduct a patent search of your own, the USPTO will put your application through a limited search when they're evaluating it. They may approve your application and grant your patent after the examination. However, this evaluation process isn't as extensive as professional patent search services, leaving you vulnerable to an infringement lawsuit if another patent-holder notices a conflict. The cost of doing a professional search first may be worth it to avoid such lawsuits.

When professional search results indicate that your idea or gadget is novel, don't let your search go to waste. File your own patent application right away. You might even prepare your application in advance so that it's ready to submit as soon as you get the results. The USPTO receives more than a thousand applications each day, so don't let someone else patent your invention before you do.


Patent Search Tips

There are many patent search tools out there, and each one has its own search parameters. To get the most of out of your search, be sure to familiarize yourself with these tools.

When tackling a patent search on your own, look for tips on how to use your chosen patent search tool. For example, FreePatentsOnline includes a search tutorial with information about using wildcards, Boolean operators and other techniques to enhance your search. If you're searching at a public facility, ask the reference librarians for tips or attend a training session. After you're familiar with your search tools, use them as appropriate for the type of search you're working on.

A novelty search explores prior art, defined earlier in this article. Search results could include any patent or non-patent documents from any time period since there are no date constraints on what constitutes prior art. If you're doing a novelty search, focus on specific patent classifications and subclasses plus keyword searching [source:, "Professional"].


A state-of-the-art search takes a broad look at what's being patented in a given field, providing a profile of the technological advancement in that field. As you would when doing a novelty search, include both active and expired patents and narrow your results with classifications and keywords. In addition, use a set of criteria to define your search and to identify results by their relevancy: For example, those that are most recent or that include some specific feature. As mentioned previously, this is the type of search that is most helpful to R & D groups as they design and develop products for a given field.

An infringement search looks for patents on a product or service for which someone already holds legal claim, either by an older patent or because the object was previously made and sold to the public. If you're doing an infringement search, focus on the details of the object or idea in question. Such searches often precede infringement lawsuits against the grantees of those newer patents [source: Cardinal IP].

A validity search seeks older patents for a given product or service that could invalidate a more recent patent. In contrast to an infringement search, a validity search might be prompted by the threat of a lawsuit from someone else. If you're doing a validity search, you may have more information available to narrow down your search, such as the names and locations of patent grantees.

Now that you have a better understanding of the challenges, costs and requirements of patent searches, you'll know what to do when genius strikes -- and in all sorts of patent-related scenarios.

Read on for even more information on staking a claim on your great new ideas.


Frequently Answered Questions

How do I do a patent search for free?
There are a few ways to search for patents for free. One way is to go to the United States Patent and Trademark Office website and use their search tool. Another way is to use Google Patents.

Lots More Information

Related Articles


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  • "Patent Search." Legal Advantage. (Jan. 23, 2011)
  • "Details about our Validity/Invalidity Search." (Jan. 23, 2011)
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