The European Student Identifier (ESI) is a digital identifier enabling students to uniquely identify themselves when they access student mobility services online; the ESI supports and eases international student mobility and trans-national cooperation of higher education institutions.
An article on how to deploy ESI at your institution can be found here and here.
Please note that the MyAcademicID team revisited the format of the previous ESI (developed by the European Student Card Project) and published the new ESI format specifications with the aim to better support online flows. Higher education institutions using the previous ESI format specifications for issuing European Student Cards will be able to continue doing so for this purpose, while adopting the new ESI format specifications for the identity federation and Erasmus services.
Making the European Student Identifier available as an attribute is a task where the IT team of the university needs to be involved. The technical information can be found at the Géant Wiki with information about the European Student Identifier: https://wiki.geant.org/display/SM/European+Student+Identifier