This site covers more than 9 million patent documents from US, Europe, Australia and WIPO. The site also offers details on over 68 million DNA and protein sequences disclosed in patents. A must-visit for any inventor’s prior art search, IPTeL recommends all researchers to try this database out.
lens.org
A simple patent search database, freepatentsonline.com offers to chemical researchers a unique way of searching for patent documents. Normalized chemical formulae can be used as search terms during a prior-art search.
freepatentsonline.com
It indexes more than 87 million patents with full text from the patent offices of over 17 different countries.
Google Patents
Access to the file histories of related applications from participating IP Offices, which currently include the IP5 Offices (USPTO, EPO, JPO, KIPO, and SIPO).
Global Dossier
Patent offices around the world allow free searching of their archives. Here, we list web page links of the patent databases of some of them.
This is the link to the database of the US Patent and Trademark Office.
patft.uspto.gov
This is the official database of the European Patent Office.
ep.espacenet.com
This link takes you to the WIPO PCT database.
wipo.int
This link will connect you to the searchable databases of the Indian Patent Office (inPASS).
https://ipindiaservices.gov.in/publicsearch
There are specialized databases exclusively meant for prior-art searches. These databases however have to be subscribed to, for access. Here, we provide you links to a few of their websites.