Public domain  -  something which is in the public domain can be freely used by the public because it is outside of intellectual property (IP) protection.  Either the IP protection was not sought or received, or the IP protection has expired.

Patents  -  afford protection for the invention defined by the claims of an issued patent for the limited term of the patent.

Patent applications  -  afford no IP protection themselves, and instead only the potential of a patent possibly being issued from a non-provisional application.

Patent applications  -  are at least initially confidential and not available to the public. 

A provisional or non-provisional patent application can be filed while maintaining confidentiality, (until . . . ):

• Patent applications are not available to the public, (until . . . )

• Patent applications are held in the strictest confidence by the USPTO, (until . . . )

• Any publicity about any recent patent application filing is derived from private sources (usually the owner) and the USPTO will neither confirm nor deny such reports.

• Therefore the filing of a patent application does not, in and of itself, have any impact on confidentiality and any trade secret maintenance.

The first "until" event triggering availability, i.e., public access to a patent application:

• The USPTO publishes non-provisional patent applications 18 months after the effective filing date, (unless . . .).

• If priority is claimed from a provisional application, the 18-months-to-publication count starts at on the provisional filing date (so publication might come 6 months after the actual non-provisional filing date).

• Unless the applicant files a request for non-publication together with the non-provisional application when filed.

• A non-publication request cannot be filed after the non-provisional application is filed, and cannot be filed if a counterpart filing in a country with an 18-month-publication rule is intended.

• Therefore confidentiality and trade secret protection can be maintained on disclosures in a U.S. patent application until the 18-months-from-filing-date publication triggers public access, and longer if non-publication of the non-provisional application is requested when it is filed.

• The filing of a provisional application in and of itself never destroys confidentiality and trade secret protections.  Provisional applications themselves are neither examined nor published.  (The publication of a non-provisional application claiming priority from a provision will trigger public access to that provisional application.

The second "until" event triggering availability, i.e., public access to a patent application:

• The issuance of a U.S. patent triggers public access to all disclosures in the patent application, and to all disclosures in earlier applications (provisional or non-provisional) from which filing date priority is claimed for the patent.

• The issuance of a U.S. patent destroys all confidentiality and trade secret protection for the disclosures therein, absolutely and for all time.

• A. U.S. patent cannot be issued without the applicant's awareness.  The applicant can still elect confidentiality and trade secret protection over patent protection after patent-application allowance, by abandoning the patent application before issuance.