I recently answered a question on Quora that asked “What does a WO patent mean?” Here was my answer:
“WO” is a prefix for WIPO (“World Intellectual Property Organization”). WIPO is an agency of the United Nations that helps regulate how patents are filed in WIPO member countries. There are about 180 WIPO countries and that list includes just about any country you would want to file a patent in.
A patent application that is stamped “WO” is simply a patent application filed with WIPO. This patent application does not have an protective rights and will never issue into a patent without further action being taken by the applicant. It’s merely the first step someone could take in filing a patent in a WIPO country.
The advantage of filing a WIPO patent application is that it preserves your priority date in all WIPO countries. In other words, if you chose to file a patent application in 10 WIPO countries based off of a WIPO patent application, each of the 10 patent applications will have the filing date of your original WIPO application.
The “WO” patent application must be “nationalized” in a member country and granted before it becomes an issued patent. The patent application is then only an issued patent in the country it was nationalized in.
Therefore, if you see a patent application (which looks a lot like a patent) that is designated “WO”, you need to explore whether that application was nationalized in a WIPO country. You can find out what countries that patent application has been nationalized in be investigating the record to see what applications claim priority to the “WO” patent application.