Important reminder: A comprehensive search for prior art includes a search for both granted patents and patent applications (which may never have been granted) in both the US and international databases. You may also need to search for scholarly articles and other venues for possible public disclosure.
USPTO Patent Public Search The Patent Public Search tool is the web-based patent search application that replaced internal legacy search tools PubEast and PubWest and external legacy search tools PatFT and AppFT. Patent Public Search has two user selectable modern interfaces that provide enhanced access to prior art. The new, powerful, and flexible capabilities of the application will improve the overall patent searching process.
Global Dossier This database allows users to see the patent family for a specific application, containing all related applications filed at participating Intellectual Property Offices (USPTO, EPO, JPO, KIPO, and SIPO).
Patent Center This database contains documents associated with a patent application. For patent applications filed after 6/30/2003, you can view the Image File Wrapper for a patent application and view the patent examiner's search strategy, communications, office actions, and other relevant documents. For patent applications prior to 6/30/2003, you can view other information regarding the patent application.
Official Gazette for Patents This link contains the most recent 52 weekly issues of the Official Gazette, published every Tuesday. You can browse by classification code or type of patent. All issues published since July 2, 2002 can be downloaded from the USPTO Open Data Portal.
Plant Patent Databases (Note: Color images vary in quality due to scanners, browsers, screens, etc., and these databases should only be used for preliminary searching)
Plant Patents Image Database (University of Maryland)
US Patent: Index to Plant Patent Color Images (New York Public Library)
Google Patents This database provides full-text searching of U.S. and many foreign patents, but is not as up-to-date as the databases maintained by the patent offices. The familiarity and ease of the Google platform may make it useful for preliminary explorations before you search in other patent databases.
PatentLens A free, open access, global patent search database with over 134 million patents from over 95 different jurisdictions.
Esp@cenet is a network of Europe's patent databases from the European Patent Office (EPO)
PATENTSCOPE from the World Intellectual Property Organization (WIPO)
Korean Intellectual Property Rights Information Service (KIPRIS)
China National Intellectual Property Administration (CNIPA) from the People's Republic of China