The ISSN (International Standard Serial Number) is an eight-digit number which identifies periodical publications as such, including electronic serials. More than one million ISSN numbers have so far been assigned.

It is managed by a world wide network of 85 National Centres coordinated by an International Centre based in Paris, backed by Unesco and the French Government. The ISSN is used by various partners throughout the information chain: libraries, subscription agents, researchers, information scientists, newsagents (through its barcode version).
The world database of ISSN numbers (and the corresponding bibliographic records), known as the ISSN Register, is available through a Web interface, The ISSN Portal, which may be freely evaluated and tested for a period of one month. The ISSN products may be subscribed to through our order form.

Publishers or other interested parties (libraries, documentation centres...) may request the assignment of an ISSN to a given periodical, if it does not yet have one.