Are you a reader who looks to see which year your books were published? You may have noticed a strange series of digits near the publication date on each book’s copyright page. Those digits make up the ISBN. Unless you already work in the book industry or education sector, you’re probably not familiar with this number.

It can be helpful to know what an ISBN is! Plus, knowing how it’s composed will make it less mysterious. Some of you use it every day but don’t know exactly why the digits are arranged that way. The first thing to understand is that the numbers aren’t created randomly. Their positioning has a reason and purpose.

Whether you’re a weekend reader who likes to discover new books, a teacher looking for class material, an author interested in self-publishing or a bookstore employee checking inventory, you’ll benefit from knowing how to use the ISBN.

### Unique international identifier

ISBN is an acronym for International Standard Book Number. It’s a unique series of digits assigned to every book published in the world. Each different edition of the same book has its own ISBN. That means the paper-format, digital, illustrated or translated versions of the same book have different ISBNs. Every time a book is republished, it’s assigned a new ISBN.

### What is the ISBN used for?

The main purpose of the ISBN is to facilitate database management for anyone involved in the book industry. The same book may be published in multiple editions and even by different publishers. Thanks to the ISBN, publishers, printers, distributors, booksellers, librarians and copyright collectives can be sure they’re referring to the right edition and aren’t making mistakes when it comes to tracking sales or royalties.

The ISBN also makes it easier for people in the book industry as well as consumers to search for books. Many books have identical or similar titles. Looking up a book by its title can sometimes be a complex task. Numerous similar results may be shown. Whether you’re a librarian or a graphic novel collector, you can be sure you’re getting the edition you want when you use the ISBN.

### What is the ISBN’s format?

The ISBN comes in two different formats: ISBN 10 and ISBN 13. It doesn’t really matter which one you use. When the ISBN was created in 1972, it contained only 10 characters. By the early 2000s, the 10-character format was running out of available combinations. A new format was needed.

In 2007, the 13-character ISBN became compulsory for all new books. All ISBN 10 combinations were also converted into the ISBN 13 format at that time. ISBN 13 was based on EAN (European Article Numbering), which is the series of numbers appearing below product barcodes.

The digits making up the ISBN aren’t random: complex mathematical formulas are used to determine them!<

#### ISBN 10 format

This format contains 4 series of characters, for a total of 10 characters. Each series has its own significance in identifying books. The series are separated by dashes. The series sequence is therefore A–B–C–D.

- A: In general, the first series represents the geographic zone where the book was published. Geographic zones sharing the same language usually use the same digits. For example, 0 and 1 are used for English-speaking areas such as the U.S. and U.K. while 2 is used for French-speaking areas such as France and Belgium. Publishers in Canada can choose which of those two zones they want to belong to, depending on whether they publish primarily in English or French.

- B: This series is variable in length and is assigned to a specific publisher. Two publishers with the same zone number (series A) cannot use identical digits in series B. Publishers that produce large numbers of books will have a shorter combination of digits in series B in order to free up more combinations in series C.

- C: This series is variable in length and identifies the specific edition of a book. A publisher that wants to develop a catalogue of 99 books will need 2 digits in its series C while a publisher that intends to a develop a catalogue of 9,999 books will need 4 digits in its series C. Publishers with more digits in their series C will therefore have fewer digits in their series B.

- D: This series contains only one character, either a digit between 0 and 9 or the letter X. Series D is a check digit calculated using the digits preceding it. The calculation is as follows:

( x_{1} + 2x_{2} + 3x_{3} + 4x_{4} + 5x_{5} + 6x_{6} + 7x_{7} + 8x_{8} + 9x_{9} + 10x_{10} ) = 0 (mod 11)

The result is always between 0 and 10. If the result is 10, the check digit becomes an X so the 10-character format can be maintained.

#### ISBN 13 format

ISBN 13, which has been compulsory since 2007 and is based on the EAN, usually starts with the series 978, representing the EAN code for books.

That sequence is followed by the first 9 digits of the ISBN 10, consisting of series A, B and C. Those series are composed the same way they are for ISBN 10.

The 13th character is a single check digit between 0 and 9 determined according to a complex calculation:

(x_{1} + 3x_{2} +x_{3} +3x4 +x_{5} + 3x_{6} + x7 + 3x_{8} + x9 + 3x_{10} + x_{11} + 3x_{12} + x_{13}) = 0 (mod 10)

The ISBN 13 format is therefore: 978–A–B–C–D.

### How can you obtain an ISBN?

ISBNs for English-language publishers in Canada are managed by Library and Archives Canada, which issues ISBN prefixes starting with 0 or 1.

For French-speaking areas (digit 2), the ISBNs are administered by the *Association francophone pour la numérotation internationale du livre* (AFNIL). For French-language publishers in Quebec and the rest of Canada, AFNIL is represented by *Bibliothèque et Archives nationales du Québec* (BAnQ).

BAnQ will give you a free ISBN prefix corresponding to the series 978–A–B. The combination you’ll be assigned will be unique to you as a publisher. Your ISBN prefix comes with a set of numbers for your books, covering all the possible combinations for series C and D.

### Other unique identifiers

Other categories of works can be assigned unique identifiers. For example, sheet music collections have an ISBN as well as another 13-digit number called the ISMN (International Standard Music Number). You can obtain an ISMN from Library and Archives Canada.

Periodicals such as newspapers, magazines and directories are assigned an ISSN (International Standard Serial Number), which is an 8-digit identifier. In Canada, ISSNs are administered by Library and Archives Canada. In addition, some magazines are given a different ISBN for each issue.

The final type of unique identifier is the ISNI (International Standard Name Identifier) , which is a 15-digit number identifying creators. It’s relatively new and not yet widely used but its purpose is to avoid errors when identifying creators and especially to differentiate between those with similar names.

**Also in the Did you know category : legal deposit **