How to patent search:
How do I do a patent search using free online patent databases

ATMAC Last update: Apr. 3, 2021

Patent searching

Before spending your hard-earned money on engaging a patent agent and applying for a patent, you should be confident that your idea is both commercially valuable and likely to be patentable.

For the purposes of this article, we will assume that you have already determined that your idea is commercially valuable and would be worth the investment in patenting. The question then remains of whether your idea is “different enough” in comparison to the prior art in order to be patentable. That’s where patent searching comes in.

Searching patent databases before you file a patent application is extremely useful and strongly recommended. Here are two reasons why:

  1. A good search may uncover the fact that your idea has already been invented. Searching can thus save you from wasting money applying for a patent that you will not get.
  2. Equally beneficial, a search may also show that certain aspects of your invention are not novel but other aspects may be. Knowing these differences between your idea and the state of the art before drafting a patent application is highly advantageous. The focus of the application should be on your invention’s improvements to the state of the art, not on the parts that are the same. Searching can thus focus your application on the parts of your idea that matter.
Searching before you file helps avoid unnecessary work and costs, and further helps you and your patent agent draft a better patent application.

Free searches v. Paid searches

There are essentially two ways you can do a patent search: you can search yourself, or you can pay someone to search for you.

Besides being free, searching yourself is great because you get immediate results and feedback as you go. Being the inventor, you already know your invention. You inherently know what you are searching for. With an open mind, you will be able to spot similarities and differences quickly.

Paid searches are particularly beneficial when your own searching comes up empty, but you are still worried the idea may be out there. In this case, it can be beneficial to hire someone with more experience to see what they can find. That said, it is important to remember that, unless your exact invention is found, no search will ever be “complete”. Any search that comes back indicating your invention was not found will necessarily have a big disclaimer attached to it. More about that later.

Free patent databases available online

If you are savvy with computers and have used online search engines such as Google®, you should be capable of doing at least a basic patent search. The Internet is replete with free patent searching databases. Each country’s national patent office typically has one, and several other organizations provide even better options. Here are two good ones:

  1. Espacenet by the European Patent Office
    “free access to over 120 million patent documents”
  2. Google Patents
    “over 120 million patent publications from 100+ patent offices around the world”

Many individuals worry that they do not have the experience to do an effective patent search themselves. This may be true is some cases; however, I still recommend that inventors give searching a try. The interfaces of the above two searching databases are simple to get started. You type in keywords related to the invention and press enter. Couldn’t be easier.

I’ve given some tips and a few examples for more advanced searching below, but I usually start my searches by just typing some words I think are relevant and pressing enter.

The Espacenet and Google Patents databases have essentially the same content. From my experience, there is not really much difference between the search results on the two platforms. I prefer using Google Patents and usually start there; however, I sometimes switch over to Espacenet to get a second opinion.

For the rest of this article, I’ll primarily focus on using Google Patents to do your search, but the same techniques apply equally to Espacenet so feel free to try both.

Will Google steal my idea?

Some individuals worry that their idea may get stolen if they search online. They especially worry that Google will steal their idea if they search on Google Patents. Although I cannot definitively say that this will not happen, I highly doubt it. The number of queries they receive is immense. Also, keywords related to an idea are not equal to the idea itself. If you are really worried about it, you could also throw them off track by searching for other unrelated things at the same time.

I can speak to practical matters though. I simply do not know of any searchers who have their own private database. All searchers of whom I am aware search in shared databases run by an external organization such as Google. Searching online databases involves sending keywords related to the invention to the database’s interface. If you hire someone to search for you out of fear that Google will steal your idea if you search yourself, it’s highly likely the person you hire will simply query Google instead. Regardless of whether you search yourself or hire someone, keywords about your invention will inevitably be sent to an online database.

Worried about finding your invention online?

Do not let nervousness about finding your invention stop you from actually trying to find it.

I have had numerous inventors inform me with absolute certainty that their idea is new. They assure me they have searched rigorously and found nothing even remotely similar. It was somewhat embarrassing for them to hear that I found their exact idea within the first minute of searching simply by using three or four keywords taken from their self-selected title of invention.

I want to be clear that I am not criticizing these inventors. Inventors do not want to find their invention online. I get it. I have invented things myself and I know the feeling. I am just noting this to the reader for the purposes of making you aware of your innate bias. Although you love your idea, it is in your best interest to be as open-minded as you can to the possibility that someone already thought of it. The earlier you find out, the better.

Finding your idea in a search is disappointing for sure but think of the time and money you just saved. Do the best search your can. Avoid deliberately not finding your idea just to keep your dream alive. Keep digging.

What to search for

The goal of doing a search is to help you and your patent agent make informed decisions regarding patentability of your invention.

At a high level, an invention that is patentable will have: 1) a difference with the prior art and 2) that difference will be non-obvious in view of the prior art. When you are searching, you are trying to find prior patents and publications that disclose ideas that are the same or similar to yours.

If you find something exactly the same, including all the features and options you thought of, you can stop searching and give up on patenting your idea. It is simply not possible to get a patent on something that is already known to the public.

If you find prior art documents that disclose technology that has similarities to your invention but is still different to your invention, make a note of these documents and the differences for discussion with your patent agent. Your patent agent will be able to advise you on whether the differences are “enough” for patenting success. The test is whether the difference would have been obvious to a person skilled in the art, but the case-specific details really matter. This is a perfect topic to discuss one-on-one in a confidential patent clarity session.

How to search

At a high level, searching boils down to looking for keywords in documents. One trick to a good search is figuring out what keywords are important and filtering your search parameters to focus on documents using those keywords in the right context.


To search for your invention, you’ll need to select keywords related to your invention. Keep in mind there may be multiple ways to refer to a part or concept so you should try to include synonyms of which you are aware. One way to get ideas for keywords is to think of a “1-sentence description” of your invention. Brainstorm different versions to get more keywords.

Once you’ve got some initial keywords, try entering them into the search field of the online database. When you type them in, it’s okay to simply type the words one by one separated by spaces. By default, the search engines will treat spaces as a logical AND, which means that the documents returned will each include all of the keywords you entered.

Here’s an example utilizing the Google® Patents database:

Google patent search example

This search will search for patent documents that include all four words: pole, jump, grip, and sensor.

If you have a particular phrase that includes multiple words that go together, e.g., “ice pick”, you can enter the phrase in quotes to ensure the database searches for the phrase as a whole.

“ice pick” hollow actuator

This would search for patent documents that include the phrase “ice pick” and also include the words hollow and actuator.

Advanced searches

Depending on the field of technology and keywords of your invention, you may get some interesting hits right away or you may get a bunch of documents that seem totally unrelated.

If the results list is huge or not related to your invention, you will likely need to further limit the search and/or order the results to place more relevant documents higher in the list. Here are some ways you can do this:

  • Add more keywords
  • Use Boolean logic
  • Use proximity operators
  • Search in specific parts of the document
  • Filter by classifications
  • Use wildcards

Note - For using Boolean logic on Google® Patents, you’ll need to click the “Advanced Search” link at the bottom of their home screen.

Google patents advanced search

The direct link to Advanced Search is here:

Also, the help for Google patents is accessed by clicking the “About” link at the bottom of the screen. (It took me a bit of time to find that myself.) They provide short, easy to read examples of using various search parameters here.

To get you started, I’ll cover the three searching parameters that I most use: Boolean logic, proximity operators, and classification filtering.

Boolean logic

Boolean logic can be used with connector words such as AND / OR / NOT (always write these in capital letters) to join some or all of your keywords together using brackets in desired combinations. (Again – make sure you are in the Advanced Search on Google Patents for using Boolean operators.)

(safety OR seat) AND belt

This will match documents and rank them higher in the list when they include the term “safety belt” or the term “seat belt”. By default, the connector word of AND is always used whenever you separate words by a space, so it is generally not necessary to keep including the word AND between all words.

(pet OR animal) “restraining device” lure NOT fish

This will match documents for “pet restraining device” or “animal restraining device” that include the word “lure” but do not include the word fish.


Proximity operators rank documents higher when the keywords are found near / adjacent to one another by some number of words. Proximity operators do not actually change which results are found; instead, they change the order of the found documents. Documents that meet the proximity requirements are ranked higher on the results list.

Two examples might make this easier to understand:

hammer NEAR/5 “pressure sensor”

This ranks documents higher in the results list when the word “hammer” and term “pressure sensor” are near each other in any order by up to 5 words (i.e., hammer comes either before or after pressure sensor by up to 5 words).

hammer ADJ/5 “pressure sensor”

This ranks documents higher in the results list when the word “hammer” and the term “pressure sensor” are adjacent each other in the same order as specified by up to 5 words (i.e., hammer comes before pressure sensor by up to 5 words).

The main difference between the NEAR and ADJ proximity operators is whether the words must be in the same order that you put or if they can be in either order. NEAR means any order; ADJ means in the order you used in the search box.


When patent applications are filed, they are classified by the patent office into one or more classifications, sometimes referred to as classes. Each classification pertains to a specific type of device or process defined by its technical features. High level classifications are subdivided into subclasses, which are again subdivided. The classes form a tree, with different branches representing different types of technology.

Classifications are beneficial to searching because you can filter your search only for one or more classifications that are relevant to your invention. Likewise, you may also simply browse all the patents classified into a particular subclass if it is very likely your type of invention would be classified in that subclass.

The trick with classification searching is finding the relevant classifications. The Cooperative Patent Classification (CPC) is a patent classification system used by the European Patent Office (EPO), the United States Patent and Trademark Office (USPTO), and the Canadian Intellectual Property Organization (CIPO). This system is hierarchical where the top-level classes include these nine categories:

  • A: Human Necessities
  • B: Operations and Transport
  • C: Chemistry and Metallurgy
  • D: Textiles
  • E: Fixed Constructions
  • F: Mechanical Engineering
  • G: Physics
  • H: Electricity
  • Y: Emerging Cross-Sectional Technologies

Each of those top-level classes contains many subclasses, which each may themselves contain any number of subsubclasses, etc.

The European Patent Office provides a free online tool to help search through the classification hierarchy itself to find relevant subclasses that may then be explored.

EPO patent classification search

The link to this searching tool is found here:

Besides searching through the classifications themselves, another way to find relevant classifications related to your invention is to first find one or more related patent documents. The cover page of the patent documents themselves will include an indication of the CPC classifications under which that technology falls. You can then go and browse for other patents or do keyword searches as appropriate under those specific subclasses.

The Advanced Search of Google Patents lets you do classification filters by just including them without any special syntax:

soil ADJ/5 sensor A01B

This search would require documents to have both the words “soil” and “sensor”, rank the documents higher if the words are in that order within 5 words of each other, and limit the search only to patent documents that are classed under the following class:

finger ADJ/5 sensor G09C

This search would require documents to have both the words “finger” and “sensor”, rank the documents higher if the words are in that order within 5 words of each other, and limit the search only to patent documents that are classed under the following class:


Invest a bit of time – it’s well worth it

If you have never searched before, you may want to allocate about 30 minutes to first play around with the searching interface and perhaps read a bit of the online help before really beginning searching in earnest. Or just dive in and read the help later if you get stuck.

Bottom line - there are many searching options and ways to search. I’ve only scratched the surface in this article so feel free to explore the user interfaces and experiment.

Reviewing the results

When your searches result in hits that initially sound similar to your invention, you’ll need to review those documents to see if they actually are the same. It is common for keywords to hit on unrelated documents – you won’t know until you review the documents.

One trick I like to use on Google Patents is to middle-click on the patents I want to review so they open in a separate web browser tab. Middle-clicking means to click using the middle mouse button. You can also right-click on the patent link and then select “Open in New Tab” to achieve the same thing. Opening in a new tab allows you to quickly review the patent document without losing your place in the search results.

While searching, keep notes of the patent numbers you find that disclose technology similar to your invention.

The searching process is iterative in nature – as you find interesting documents those may lead you to find others. However, after a while, you may find that your searches are no longer bringing back anything more than what you have already found. At this point, depending on how confident you are feeling about the results, you may either brainstorm new keywords or classifications, or you may end the search.

When you are finished your searching, you should have a short list of prior art patent documents that disclose similar technology to at least some aspects of your invention. You should also have a list of one or more features that you could not find in any of the prior art documents that you want to discuss with your patent agent. At this step, you're in a great position to book a patent clarity session.

Disclaimers on searches

The last thing to mention about searches is that not finding your invention does not mean your invention is new or patentable.

Absence of evidence is not evidence of absence.

Regardless of whether you do your own searching and/or hire a professional, a patent search is not an absolute measure of patentability and there can never be a guarantee that a patent will be granted and valid. Only the applicable patent offices, e.g., United States Patent and Trademark Office (USPTO) / Canadian Intellectual Property Office (CIPO) / etc., and/or the courts can definitively determine patentability of an invention. Thus, it is probable that the patent office(s) will use patents in office action rejections that are different from those located during your search, some of which may be closer to the subject invention than those located in your patentability search.

Prior art searching is an imprecise art and relevant references may be missed. The sheer numbers of patent documents make it impossible to review all documents. For instance, as shown above, the Cooperative Patent Classification (CPC) is divided into nine sections, A-H and Y, which in turn are sub-divided into classes, sub-classes, groups and sub-groups. There are approximately 250,000 classification entries. Not all the correct classifications may be searched. Likewise, there are over ten million granted US patents alone, not including published applications and other country’s patents and applications. There are over 152 contracting states to the PCT, most with a respective Patent Office, plus additional patent offices and of course non-patent documents such as articles and plain old books. It is highly likely that not all relevant documents will be found in a search. It is also possible that you or the searcher will mischaracterize or otherwise miss technical features disclosed or implied in the reviewed prior art documents.

To make matters even worse, patent applications are typically subject to a secrecy period, often of 18 months from their filing date. Therefore, a prior art search cannot uncover patent applications that have been filed within the previous 18 months unless the owner requested earlier publication.


Despite these disclaimers, searching can still be an incredibly valuable exercise to go through – even if you, the inventor, simply spend a few days doing due diligence searching on your own. You will get familiar with the state of the art doing searching and you may be surprised at how similar your idea is to what is out there already. Although it can initially feel disappointing, this information can only help you in the long term.

Feel free to reach out if you need any assistance with your searches or if you would like to discuss your search results with a registered patent agent. If you have already done your own searching and have identified possible points of patentability, you may be ready to invest in a confidential patent clarity session.

- Andrew MacMillan
Registered patent agent and founder of ATMAC Patent Services.