Regex for ISBN — Pattern Explained with Examples

International Standard Book Numbers (ISBN) uniquely identify books and other publications. This pattern validates both ISBN-10 (10 digits, last may be X) and ISBN-13 (13 digits beginning with 978 or 979) formats with optional hyphen separators.

The Pattern

# ISBN-13
/^(978|979)\d{10}$/

# ISBN-10
/^\d{9}[\dX]$/

Pattern Breakdown

Matches

• 978-3-16-148410-0
• 0-306-40615-2
• 9780141036144
• 0306406152
• 9791090636071

Does NOT Match

• 978-0-306-40615 (wrong length)
• 123456789
• 97812345678901 (too long)
• 978ABCDEFGHIJ
• 0-306-40615-X (hyphen before X is misplaced)

Language Examples

JavaScript

const isbn13Regex = /^(978|979)\d{10}$/;
const isbn10Regex = /^\d{9}[\dX]$/;
console.log(isbn13Regex.test('9780141036144')); // true
console.log(isbn10Regex.test('0306406152'));     // true
console.log(isbn13Regex.test('123456789'));      // false

Python

import re
isbn13 = r'^(978|979)\d{10}$'
isbn10 = r'^\d{9}[\dX]$'
print(bool(re.match(isbn13, '9780141036144')))  # True
print(bool(re.match(isbn10, '0306406152')))      # True
print(bool(re.match(isbn10, '123456789')))       # False

Common Pitfalls

• Hyphens are optional in ISBNs but their positions carry meaning (group, publisher, title, check digit) — strip hyphens before validation or use a more complex pattern with hyphen validation
• ISBN-10 check digit can be X (representing 10) — this is valid and must not be rejected
• ISBN-13 prefixes are limited to 978 and 979 — other 13-digit numbers starting with different prefixes are not valid ISBNs
• Structural validation does not verify the check digit — real ISBN validation requires computing the check digit using the weighted modulo algorithm (mod 11 for ISBN-10, mod 10 for ISBN-13)
• Some older books have only ISBN-10; after 2007 all new ISBNs are issued as ISBN-13 — support both for legacy catalog data

Real-World Use Cases

• Library catalog systems — validate ISBN entries when adding new books to a database
• Bookstore inventory — verify scanned barcodes (which encode ISBN-13) before looking up product details
• Book trading platforms — validate user-entered ISBNs before listing books for sale or trade

FAQ

Related Patterns

Regex for Numbers Regex for UUID