What is the confidential nature of international patent applications under the Patent Cooperation Treaty (PCT)?

International patent applications filed under the PCT are generally kept confidential and not made publicly available before international publication, which occurs soon after the expiration of 18 months from the priority date, according to PCT Article 21(2)(a). The International Bureau and International Searching Authorities are not allowed to give access to the application to any person or authority before publication unless requested or authorized by the applicant, with some exceptions.

As stated in MPEP 110:

“Although most international applications are published soon after the expiration of 18 months from the priority date, PCT Article 21(2)(a), such publication does not open up the Home Copy or Search Copy to the public for inspection, except as provided in 37 CFR 1.14(g).”