- Free users are non-registered users accessing the Portal on the Internet. They have access to “essential” identification information, referred to as “Released ISSN data” for Confirmed records.[see section 2.2. What does "Released ISSN data" mean? and section 2.5. What types of ISSN records are accessible in the ISSN Portal?]

- Corporate users are users in institutions having subscribed to the ISSN Register. They register either by login/password or by IP. They can access all information from all types of ISSN records. However, the amount of data they will be entitled to download depends on the subscription package chosen by their institution.

- Network users are users in National Centres and at the International Centre. Network users access the same kind of data and services as corporate users, and they also access administrative data.

- Both Corporate users and Network users are Subscribing users.

- Publishers are users requesting ISSN assignment, and other services for publishers, from the ISSN International Centre. Even though they need to register to the ISSN Extranet, they are not considered Subscribing users in the Portal: they do not have access to full ISSN information, except for records of resources under their responsibility [see sections 8.4 ISSN Assignment and 8.5. ISSN Claiming and transfer of ownership].