What is a prior art search and how to do it?

If you’ve ever wondered how to find out whether your invention is truly new before filing a patent, you’re thinking about a prior art search, one of the most important steps in the entire patent process.

A proper prior art search helps you avoid wasted patent filing costs, identify your competition, and understand whether your invention meets the novelty and non-obviousness standards required by law.

This guide covers what prior art is, why searches matter, how to perform one using official government databases, what examiners look for, and how businesses can integrate it into their innovation strategy.

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TL;DR: ‍

• Prior art is any public information that existed before your patent’s filing date including patents, publications, products, or public use.
• Purpose: To check if your invention is new and inventive before filing a patent.
• Where to search: USPTO Patent Public Search, EPO’s Espacenet, WIPO PATENTSCOPE
• Timing: Ideally conducted before filing a patent, but also useful during examination or before product launch.
• Tip: Use both keyword and classification (CPC/IPC) searches for the best results.
• Risk: A weak or incomplete search may lead to rejection or infringing on existing patents.

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What is prior art?

The United States Patent and Trademark Office (USPTO) defines “prior art” as anything that was patented, described in a printed publication, in public use, on sale, or or in any other way available to the public before the effective filing date.

The European Patent Office (EPO) defines it as everything made available to the public “in any way, anywhere in the world” before the filing date.

In practice, prior art covers:

• Published patents and patent applications
• Scientific articles, theses, or standards (organizational specifications)
• Websites, videos, manuals, and public talks
• Commercial products or public demonstrations

If it was publicly accessible, it can count as prior art regardless of the language or country.

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Why a prior art search matters

A thorough prior art search brings both legal and strategic value to inventors and companies:

• Determines patentability: Helps assess whether your invention is new and non-obvious before investing in filing fees.
• Saves costs: Filing a patent can cost thousands, so early searches prevent wasted applications.
• Improves applications: Knowing existing technology helps draft stronger, more focused claims.
• Guides R&D: Identifies “white spaces” areas open for innovation.
• Avoids infringement: Ensures your product doesn’t overlap with someone else’s patent rights.

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When to perform a prior art search?

You can (and should) perform a search at several stages:

• Before filing a patent (to evaluate novelty).
• During prosecution (to respond to examiner rejections).
• Before product launch (freedom-to-operate analysis).
• Before acquisition or licensing (to verify patent validity or scope).
• Post-grant (which will be covered later) 

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What are the types of prior art searches?

Not all patent searches serve the same purpose. Each type answers a different question about your invention or business goals, which is why it’s important to know when and why to use them.

Patent offices typically classify searches into four main types:

1. Novelty search: This determines if your invention is new before you file a patent.
2. Freedom-to-operate (FTO) search: Ensures your product can be made or sold without infringing others’ patents.
3. Invalidity (or opposition) search: You can find earlier disclosures that could invalidate an existing patent.
4. State-of-the-art search: You can review existing technologies in a field for R&D or competitive intelligence.

Each type is different, but all rely on identifying publicly available information that predates the filing date.

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Where to perform a prior art search?

You can use official, free patent databases maintained by the world’s major patent offices:

• USPTO Patent Public Search (PPUBS): Full-text U.S. patents and applications, advanced Boolean and field search options.
• Espacenet (EPO): Over 150 million patent documents worldwide, including classification and citation data.
• WIPO PATENTSCOPE: International PCT applications and national data from over 70 patent offices.

These databases also link to CPC/IPC classifications, which group inventions into specific categories like chemical processes, medical devices, or software methods, so you can find related technologies more accurately and uncover results that keyword searches might miss.

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How to conduct a prior art search step-by-step

1. Define your invention clearly

Break your invention into its essential technical features. Identify its purpose, components, and unique aspects.

2. Identify keywords and classifications

List synonyms, broader and narrower terms, and relevant CPC/IPC codes (available on USPTO and EPO classification search pages).

3. Build effective search queries

Use Boolean operators (AND, OR, NOT)  as well as field tags (such as title, abstract and claims). For example, you can use AND to combine keywords and narrow results, OR to include synonyms, or NOT to exclude irrelevant topics. For even greater accuracy, use field tags to search within specific parts of a patent document. Combine keyword searches with classification filters for precision.

4. Search across multiple databases

No single database covers everything. Run your search in at least two major sources (USPTO and WIPO, or EPO and JPO).

5. Analyze and document findings

Review abstracts and claims first. Note down publication numbers, filing dates, and applicants. Keep a record of your search terms and databases used for future reference.
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What patent examiners look for

Patent examiners use similar methods but with access to specialized internal tools. Based on the USPTO’s Manual of Patent Examining Procedure (MPEP 2100) and EPO Guidelines for Examination, examiners check:

• Novelty: Whether all features of a claim appear in a single prior art reference.
• Inventive step (obviousness): Whether combining known elements would have been obvious to a person skilled in the art.
• Enablement: Whether the prior art sufficiently describes how to make or use the invention.

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Common mistakes in prior art searches‍

• Searching only in English, important prior art may exist in Japanese, Korean, or German databases.
• Relying on a single keyword or database.
• Ignoring non-patent literature (academic papers, public disclosures).
• Failing to check publication and priority dates carefully.
• Misinterpreting “patent pending” as enforceable protection.

A strong search is broad enough to uncover global results and narrow enough to focus on truly relevant disclosures.

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Why patent post-grant searches also matter

Patent searches don’t end once an application is filed or granted in fact, that’s when they become most valuable from a business perspective. You should look for new filings, infringements, competitors’ continuations, or emerging technologies that can all affect your rights. 

Why should you conduct periodic post-grant searches:

• Identify potential infringements of your own patents early, so you can enforce them.
• Monitor competing patents that might limit your freedom to innovate or require design-arounds.
• Assessing patent renewal decisions knowing which patents remain commercially relevant helps prioritize your patent renewal budget.
• Discover licensing opportunities by spotting overlaps or complementary technologies in your field.

What to look for in after-filing searches:

• Claims of existing patents: In FTO and validity searches, the specific claims matter more than broad descriptions — these define what you might infringe or challenge.
• New competitor filings: Watch for recent applications in your space that could shift competitive dynamics or limit your options.
• Expired or expiring patents: These may open up new opportunities for entry or licensing.
• Post-grant proceeding windows: In jurisdictions like the U.S., for example, a petition for post-grant review must be filed within 9 months of grant.

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When to seek professional help

While free government databases are powerful, patent attorneys and professional searchers use advanced tools like Derwent Innovation, Orbit, or PatBase. These tools can:

• Interpret claims and equivalents more accurately.
• Access non-English full-text databases.
• Provide structured reports with legal opinions.

If your invention is core to your business or you’re planning to file internationally, professional support is worth the investment.

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How PatentRenewal.com helps you with your patent portfolio

Once you’ve filed and secured your patent rights, the next challenge is keeping them active across jurisdictions.

PatentRenewal.com automates the entire patent maintenance process from monitoring due dates to executing patent renewals giving you full cost transparency and savings up to 50% compared to law firms and other IP service providers.

Our platform provides a clear online overview of all your patent renewals, integrates invoices, and ensures compliance with every patent office worldwide, so you can focus on innovation while we handle everything else. Discover how PatentRenewal.com can simplify your patent maintenance.

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FAQ about prior art searches

What counts as prior art?
Anything publicly available before the filing date including patents, publications, products, or public demonstrations.

Do I need to do a prior art search before filing?
‍It’s not legally required but strongly recommended. It helps you assess patentability and strengthen your application.
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How far back should I search?
At least 20 years, since that’s the average patent lifetime. However, older publications may still be relevant.

Are prior art searches international?
Yes. Patent rights are territorial, but prior art is global. A disclosure anywhere in the world can affect your U.S. or European application.

Can I do my own prior art search?
Yes, official databases like USPTO and WIPO PATENTSCOPE are open to everyone. Still, professional assistance improves accuracy.

Does a prior art search replace an FTO search?
No. A novelty search checks if you can get a patent. An FTO search checks if you can safely make or sell your product without infringing others’ rights.