PCT stands for Private Communication Technology, a protocol developed by Microsoft and Visa International for secure communication on the Internet. It is a counterpart to Netscape's SSL protocol and a companion to the STT protocol. Like SSL, PCT is intended for Internet standardization.

The protocol is quite similar to SSL in many respects, and in fact the message formats are similar enough so that a server can interact with clients supporting SSL as well as client supporting PCT. According to the specification, PCT "corrects or improves on several weaknesses of SSL." The following are the main differences:

PCT involves fewer messages between the client and the server than SSL, and the messages themselves are shorter.

PCT has more choices in the negotiation of algorithm and data formats than SSL, and the negotiation has additional cryptographic protection so that the client and server can verify that their choices have not been modified.