TACK is an IETF draft that allows certificate pinning for a TLS web server, provided the clients' browsers support it. Unlike the certificate pinning feature available with HSTS preloading, the server's operator is not committing to a particular certificate in the chain (and hence typically to a particular root or intermediary CA), instead retaining his own (offline) key that can be used to authorize the use of a new server TLS certificate.
Which browsers support TACK? Are there extensions to add support to browsers that do not otherwise support it?
certificate-pinning
orTLS-certificate-pinning