Techniques for password constraint enforcement used in external site authentication are disclosed. In some embodiments, password constraint enforcement used in external site authentication includes monitoring encrypted network communications between a client and an external site (e.g., a remote server), in which the encrypted network communications are encrypted using a first protocol (e.g., Secure Sockets Layer (SSL) protocol, HTTPS protocol, or another protocol for encrypted network communications); and determining if the client sends a request to create user credentials for an external site authentication. In some embodiments, password constraint enforcement used in external site authentication further includes performing password constraint enforcement used in the external site authentication.