Prior art
Also called state of the art, prior art reference, relevant prior art, existing technology
Prior art is everything made available to the public before the relevant filing date, by any means, that can help decide whether a claimed invention is new and involves an inventive step (is not obvious)1.
Patent offices judge applications against prior art, and examiners cite the prior art they rely on2. Parties challenging a granted patent also search for prior art to show that one or more claims are invalid2. The European Patent Convention calls the same body of knowledge the "state of the art"3.
What counts as prior art
Prior art is not limited to patents. US law and the EPC both cover other forms of public disclosure5,3.
- Patents and published applications. US law bars a patent where the claimed invention was already patented before its effective filing date5.
- Printed publications, including online ones. The USPTO treats an electronic publication, including an online database or internet publication, as a printed publication if it was accessible to persons concerned with the art7.
- Public use and sale. US law lists public use, sale and anything otherwise available to the public alongside publications5.
- Oral disclosures. Under the EPC the state of the art includes everything made available to the public by written or oral description, by use, or in any other way3.
- Earlier applications published later. An application filed earlier but published after your filing date can also count, under rules that differ by jurisdiction5,3,6.
The date that matters
Whether a disclosure is prior art depends on when it became public compared with the application's relevant date1,5.
- United States: the cut-off is the effective filing date of the claimed invention5. For earlier US patents and published applications, 35 U.S.C. 102(d) treats them as effectively filed on the earliest application that describes the subject matter, including a priority application5.
- Europe: the cut-off is the date of filing of the European application3. Where priority is validly claimed, the priority date counts as the filing date for this purpose (Article 89 EPC)8.
- PCT international search: relevant prior art is material made public before the international filing date1.
- China: prior art is any technology known to the public in China or abroad before the filing date (Article 22)6. Where priority is claimed, the filing date means the priority date (Implementing Regulations, Article 12 of the 2023 text; Rule 11 of the 2010 text)12,14.
How prior art is used: novelty and obviousness
Prior art is used in two tests. For novelty, the question is whether the invention already forms part of the prior art3. For obviousness, called inventive step under the EPC, the question is whether the invention would have been obvious to a person skilled in the art having regard to the prior art9; US law asks whether the differences between the claimed invention and the prior art would have been obvious to a person having ordinary skill in the art (35 U.S.C. 103)13. China's test of inventiveness also compares the invention with the prior art6.
Under the EPC, earlier European applications that were published only after the filing date count for novelty but are not considered for inventive step3,9.
Prior art rules by jurisdiction
United States
- Prior art under 35 U.S.C. 102(a)(1) covers inventions patented, described in a printed publication, in public use, on sale or otherwise available to the public before the effective filing date5.
- Under 102(a)(2), US patents, published US applications and applications deemed published under 35 U.S.C. 122(b) that name another inventor and were effectively filed earlier also count5.
- A disclosure made 1 year or less before the effective filing date is not prior art under 102(a)(1) if it was made by the inventor, or by another who obtained the subject matter from the inventor (102(b)(1)(A)), or if the same subject matter had been publicly disclosed before that disclosure by the inventor, a joint inventor or someone who obtained it from them (102(b)(1)(B))5.
- Under the current law there is no geographic limitation on where a prior public use or public availability occurs4.
- These first-inventor-to-file rules do not apply to applications filed before March 16, 2013, which remain under pre-AIA 35 U.S.C. 102 and 10310. An application filed on or after that date is still examined under pre-AIA law if it has never contained a claim with an effective filing date on or after March 16, 2013 and does not claim the benefit of an earlier application that did10.
Europe
- The state of the art comprises everything made available to the public by written or oral description, by use, or in any other way, before the date of filing (Article 54(2) EPC)3.
- European applications filed earlier and published on or after that date are also part of the state of the art (Article 54(3))3.
- A disclosure in the six months before filing is disregarded only if it was due to an evident abuse in relation to the applicant, or to display at an officially recognized international exhibition, and for an exhibition only if the applicant says so on filing and files a supporting certificate (Article 55(2))11.
China
- Prior art means any technology known to the public in China and/or abroad before the filing date (Patent Law, Article 22)6.
- Novelty is also lost if any entity or individual filed an application for the identical invention with the patent office earlier and it is published or announced after the filing date (Article 22)6.
- An invention does not lose novelty through a disclosure within six months before filing in the four situations listed in Article 24, including first exhibition at an international exhibition sponsored or recognized by the Chinese Government and first publication at a prescribed academic or technological conference6.
Questions people ask
Search before filing
Novelty Search AI Agent
An AI agent that searches prior art for your invention and compares each reference with it feature by feature.
Run Novelty SearchDoes prior art have to be a patent?
No. US law counts printed publications, public use, sales and anything otherwise available to the public5. The EPC includes written or oral description, use, or any other way of making information public3. Journal articles and other non-patent literature can therefore be prior art.
Does prior art from another country count?
Yes. PCT international search covers everything made available to the public anywhere in the world1. Chinese law covers technology known to the public in China or abroad6, and current US law has no geographic limitation on prior public use or availability4.
Can my own publication be prior art against my application?
It can. The US excludes the inventor's own disclosures made 1 year or less before the effective filing date, and also a third party's disclosure of subject matter that the inventor had already publicly disclosed (102(b)(1)(A) and (B))5. The EPC disregards a disclosure within six months only in cases of evident abuse or display at a recognized international exhibition, and for an exhibition only if the applicant says so on filing and files a supporting certificate (Article 55(2))11, and China's grace period of six months covers four listed situations6. Outside these exceptions, an earlier disclosure by the inventor counts5,11,6.
Is a web page prior art?
It can be. The USPTO treats internet and online database publications as printed publications if they were accessible to persons concerned with the art, and as publicly available as of the date they were posted7.
How it connects
Go from the term to the task
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- 01 / How-toPatentability search: a practical guideCheck whether an invention is new before you spend on a filing.Read
- 02 / AI agentNovelty Search AI AgentAn AI agent that searches prior art for your invention and compares each reference with it feature by feature.Run it
- 03 / Free toolAI prior art searchDescribe an idea, get the closest patents.Try tool
More next stepsHow to run a freedom-to-operate analysis