Fastmail This document defines version "2.0" of JSContact. It defines the "uid" property of a Card object to be optional, rather than mandatory as defined in previous version "1.0". Other than changing the "uid" property, all other definitions of JSContact version "1.0" remain as defined in RFC 9553. This document updates RFC 9555 by redefining how to convert the now optional "uid" property from and to vCard.