International Standard Serial Number

What's an ISSN?

An ISSN is an 8-digit code used to identify newspapers, journals, magazines and periodicals of all kinds and on all media–print and electronic.

What uses an ISSN?

An ISSN identifies all continuing resources, regardless of their medium (print or electronic):

Newspapers,
Annual Publications (reports, directories, lists, etc.),
journals,
magazines,
collections,
websites,
databases,
blogs,etc.

What does an ISSN look like?

The ISSN takes the form of the acronym ISSN followed by two groups of four digits, separated by a hyphen. The eighth digit is a check digit calculated according to a modulus 11 algorithm on the basis of the 7 preceding digits; this eighth control digit may be an “X” if the result of the computing is equal to “10”, in order to avoid any ambiguity.

e. g.: ISSN 0317-8471, ISSN 1050-124X

Its role is to?

To identify a publication. It's a digital code without any intrinsic meaning:

It does not include any information about the origin or contents of the publication,
nor does it guarantee the quality or validity of the contents.
The ISSN is associated with the title of the publication. If the publication is 
modified significantly, a new ISSN must be assigned.

Where's it displayed?

For a print publication, the ISSN should be shown:

Preferably, in the upper right corner of the cover,
failing that, on the pages where editorial information is shown (publisher, frequency, 
colophon, etc.).

For a publication in electronic media, the ISSN should be shown:

On the homepage or on the main menu, if it is an online publication,
on any part visible to the naked eye (microfiche header, CD-Rom or DVD label, box, 
case, etc.), if the publication is on a physical medium.
If a publication is identified by ISSN and ISBN, both of these identifiers should be 
mentioned.