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To search U.S. Patents issued since January 1976, go to http://patft.uspto.gov/netahtml/PTO/search-adv.htm. From that page, Select "All years." Type in a search expression, and then select the Search button ([Search]).

Formulating an effective search expression may require substantial thought and experimentation, because a patent document may verbalize an idea using a variety of wordings and spellings. A search should not be so overly restrictive such that it excludes relevant patents. Conversely, a search must not be so expansive such that the search results include too many irrelevant patents, making review of the results too time consuming.

For example, suppose an inventor has conceived a better mousetrap and wishes to review U.S. Patents for similar technology. First, she may simply enter

mousetrap [Search]

The search above results in 112 patents. She may then surmise that some patents may only refer to the plural, and, therefore, she enters

mousetrap$ [Search]

, wherein $ is a wildcard that allows you to find words that begin with certain letters. Mousetrap$ finds both mousetrap and mousetraps. The search above results in 129 patents. She may then surmise that some patents may use two words: mouse trap. Thus, she enters

mousetrap$ OR "mouse trap" OR "mouse traps" [Search]

, wherein the operator OR finds documents containing either the string in front of OR, or the string following OR. Group of words enclosed in quotation marks are treated as a single search term. The search above results in 258 patents. She then surmises that requiring the words mouse and trap to be adjacent may be too restrictive. Thus, she enters

mousetrap$ OR (mouse AND trap$) [Search]

, wherein the operator AND finds only those documents containing both the string in front of AND, and the string following AND. Parentheses clarify the search expression. In the absence of parentheses, all operators associate from left to right. The search above results in 3530 patents, most of which do not pertain to rodent traps. At this point, she may wish to try a more restrictive search expression, such as an expression that only finds documents having the word mouse in the Title of the Invention. Conversely, she may also surmise that some relevant documents may not have the word mouse at all, and may instead use the plural or a synonym. (See endnote 1 below). Thus, seaching may require substantial thought and experimentation.

The search results include the text of patent. To completely understand a patent, it is necessary to also see the drawings. Drawings ("images") of the patents are available, if you have the proper plug-in, which is available free of charge via www.uspto.gov/patft/help/images.htm.

The search tool described above has at least two important limitations. First, the tool only covers U.S. patents issued since January 1976. Thus, even assuming an appropriate search expression, the tool may miss many relevant documents, especially for older technologies. Second, as discussed in another article on this website, Prior Art is not limited to patents. Thus, a search limited to patents may miss many relevant Prior Art references, especially for newer technologies, such as software, in which the U.S. Patent and Trademark Office (USPTO) has not yet accumulated a comprehensive set of issued patents. Despite these limitations, this search tool is a valuable resource provided free of charge by the USPTO.


1. (TTL/mousetrap$ OR TTL/mouse OR TTL/mice OR TTL/rodent$) AND trap$ results in 198 patents, wherein TTL only finds documents having a certain word in the Title of the Invention. In addition to TTL, there are 30 other field codes documented on www.uspto.gov/patft/help/helpflds.htm.

2. To search official publications of U.S. Patent Applications, go to http://appft.uspto.gov/netahtml/PTO/search-adv.html. From that page, Select