ISSN Validator
Paste an ISSN — or a journal's masthead, or a whole list — and every ISSN in it is checked: eight characters, X only at the end, and a check digit that matches. Each result shows the arithmetic. Runs entirely in your browser; nothing is sent anywhere. Free, no sign-up.
Every ISSN-shaped number in a line is checked, so a masthead or a reference list works too. Nothing is sent anywhere.
Paste an ISSN to check its format and check digit.
How to Use the ISSN Validator
- 1. Paste ISSNs. One per line, or any text that contains them —
eISSN: 1476-4687, a journal's footer, a reference list. Every ISSN-shaped number is picked out. - 2. Read the verdict. Each ISSN is shown in standard form, NNNN-NNNC, with Valid ISSN or the exact problem: the wrong length, a stray character, an X out of place, or the check digit the other digits call for.
- 3. Open the working to see each digit's weight and product, the sum, and the remainder that gives the check digit.
- 4. Copy the valid ones. The list is de-duplicated and written in the standard form, ready for a database or a citation.
How the ISSN Check Digit Works
An ISSN is seven digits and a check character, written as two groups of four joined by a hyphen. The rule comes from ISO 3297: multiply the first seven digits by 8, 7, 6, 5, 4, 3 and 2, add the products, and divide by 11. The check character is 11 minus the remainder — written X when that is 10, and 0 when the remainder is 0. For 0378-5955, the ISSN of Hearing Research:
| Position | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
|---|---|---|---|---|---|---|---|
| Digit | 0 | 3 | 7 | 8 | 5 | 9 | 5 |
| Weight | 8 | 7 | 6 | 5 | 4 | 3 | 2 |
| Product | 0 | 21 | 42 | 40 | 20 | 27 | 10 |
The products add up to 160. 160 mod 11 = 6, and 11 − 6 = 5 — the eighth character, so the ISSN is valid. For The Lancet's online ISSN, 1474-547X, the products add up to 144, the remainder is 1, and 11 − 1 = 10, written X.
The weighting catches every single mistyped digit and every swap of two neighbouring digits. What it cannot do is say whether an ISSN was ever assigned: a valid check digit only proves the number is well formed.
Print, Online and Linking ISSNs
- One ISSN for each medium. A journal published in print and online has a separate ISSN for each version — Nature is 0028-0836 in print and 1476-4687 online. Databases and publishers label them ISSN and eISSN, or p-ISSN and e-ISSN.
- The ISSN-L links them. The linking ISSN is one of the existing ISSNs, designated by the ISSN Network to group every medium version of the title, so databases can treat print and online as one journal. It carries an ISSN-L label but is an ordinary ISSN, and passes the same check-digit test.
- A new title means a new ISSN. When a journal changes its title substantially, it is assigned a new ISSN, so the ISSN on an older article can differ from the journal's current one.
- ISSN, not ISBN. An ISSN identifies a serial — a journal, magazine, newspaper or numbered series — as a whole; issues and articles do not get their own. Books get ISBNs, and a book in a series can carry both.
Looking Up an ISSN
To find out which publication an ISSN belongs to, search the ISSN Portal, the register kept by the ISSN International Centre, where basic records are free to view. For journals cited in PubMed, the Journal Abbreviation Finder also lists print and online ISSNs.
Frequently Asked Questions
- How do I check whether an ISSN is valid?
- Weight its first seven digits 8 down to 2, add the products, and take 11 minus the remainder after dividing by 11; the result must equal the last character, with X standing for 10. Paste the ISSN above to have it checked and the working shown.
- What is the difference between a print ISSN and an online ISSN?
- They identify the same journal in different media. A journal that appears both on paper and on the web has one ISSN for each, often labelled ISSN and eISSN. Both are valid; use the one for the version you consulted, or both if your style or database asks for them.
- What is an ISSN-L?
- The linking ISSN: one of a journal's existing ISSNs, designated by the ISSN Network to tie its print, online and other media versions together. It is not a separate kind of number and passes the same check-digit test.
- Why does an ISSN end in X?
- Because the check digit is calculated modulo 11 and can come out as 10. To keep the ISSN eight characters long, 10 is written as the Roman numeral X. X can only appear in that last position.
- Does a valid check digit mean the ISSN exists?
- No. It means the number is internally consistent. Only the ISSN register can confirm that an ISSN was assigned and to which publication — search for it in the ISSN Portal.
- Where do I find a journal's ISSN?
- On the journal's website, often in the footer or the About page; in the masthead of a print issue; in library catalogues; and in the ISSN Portal. Many article PDFs print it in the header or footer of the first page.