Provisional applications are never published, while non-provisional applications are published 18 months from the earliest priority date. Note that there are also circumstances where a U.S. applicant is allowed to validly submit a "Request for Non-Publication." These circumstances listed in 35 U.S.C. Section 122(b)(2)(B)(i):
(i) If an applicant makes a request upon filing, certifying that the invention disclosed in the application has not and will not be the subject of an application filed in another country, or under a multilateral international agreement, that requires publication of applications 18 months after filing, the application shall not be published as provided in paragraph (1).
(i) If an applicant makes a request upon filing, certifying that the invention disclosed in the application has not and will not be the subject of an application filed in another country, or under a multilateral international agreement, that requires publication of applications 18 months after filing, the application shall not be published as provided in paragraph (1).