Real ISSN Validator with Checksum

ISSN: the serial publication number and its mod-11 check digit

The ISSN (International Standard Serial Number) identifies a serial publication — a journal, magazine, newspaper or other periodical — independent of language or country. Defined by ISO 3297 and coordinated by the ISSN International Centre in Paris, it is 8 digits in two groups of four, written NNNN-NNNN (e.g. 0317-8471). The validator on this page checks the structure and the check digit.

The checksum is a weighted mod-11: multiply the first seven digits by 8, 7, 6, 5, 4, 3, 2, sum them, and the check digit is (11 − (sum mod 11)) mod 11. When that value is 10 the check digit is written as X, exactly like ISBN-10.

ISSN, ISSN-L, and the linking idea

• Print vs online: a title published in both print and digital gets two different ISSNs (p-ISSN and e-ISSN).
• ISSN-L (linking ISSN): a single designated ISSN that groups all medium versions of the same title for citation and discovery.
• No semantic parts: unlike ISBN, the digits carry no publisher or country meaning — the ISSN is an opaque serial number.

Where it shows up

• Journals & databases: indexing in Scopus, Web of Science, DOAJ, SciELO, and CrossRef metadata.
• Barcodes: encoded as an EAN-13 with prefix 977 (the "Serial Number Bookland") plus a 2-digit issue add-on.
• Library systems: subscription management, union catalogues, link resolvers.
• Mock data / testing: generating checksum-valid ISSNs for catalog fixtures.

Gotchas

• The hyphen is mandatory in the canonical form: 0317-8471, always after the fourth digit.
• X is uppercase and only last: a final value of 10 is X; normalise lowercase x.
• 977 EAN ≠ the ISSN check digit: the barcode recomputes its own EAN-13 check digit and drops the ISSN's — don't confuse the two.
• Valid checksum ≠ registered: only the ISSN Portal confirms a real assignment.

FAQ

How is the ISSN check digit computed? Weights 8,7,6,5,4,3,2 over the first seven digits; check = (11 − sum mod 11) mod 11, written X when 10.

Does the print and online edition share an ISSN? No — each medium has its own ISSN, linked by a common ISSN-L.

Is ISSN the same as ISBN? No. ISBN identifies a one-off book; ISSN identifies an ongoing serial. Both use a mod-11-style check digit that can be X, but the weights and structure differ.