If you’ve ever sold a book on Amazon or browsed its vast marketplace, you’ve likely come across the terms ASIN and ISBN. Both serve as unique identifiers, but they are not interchangeable. An ASIN (Amazon Standard Identification Number) is used exclusively on Amazon to track products, while an ISBN (International Standard Book Number) is a globally recognized code assigned to books for publishing and distribution.

For authors, publishers, and eCommerce sellers, understanding these identifiers is essential. If you plan to self-publish a book, do you need an ISBN, or is an ASIN enough? Can a book have both? And how do these codes impact sales, listings, and visibility on platforms like Amazon? Let’s learn all of these and more today.

What is an ASIN (Amazon Standard Identification Number)?

Every product listed on Amazon’s marketplace is assigned a unique ASIN, a 10-character alphanumeric code that helps Amazon track inventory, manage listings, and organize search results.

For books, the ASIN is often based on the ISBN-10 (if available), but this is not always the case. If a book is published without an ISBN, Amazon will assign it a random ASIN instead. Kindle eBooks, for example, only have ASINs and do not require ISBNs.

Amazon sellers rely on ASINs to optimize product visibility, prevent duplicate listings, and track performance. 

ASINs are also essential for Amazon SEO. When a shopper searches for a book or product, Amazon’s algorithm pulls up listings based on keywords, sales data, and ASIN relevance. 

For example, if you’re selling a self-published book on Amazon KDP (Kindle Direct Publishing), the ASIN helps customers find your book through Amazon’s search system, even if you don’t have an ISBN. 

But if you plan to distribute outside Amazon, relying solely on an ASIN is not enough—you’ll need an ISBN as well.

What is an ISBN (International Standard Book Number)?

Unlike ASINs, ISBNs are globally recognized book identifiers. An ISBN is a 10-digit (pre-2007) or 13-digit (post-2007) numeric code that uniquely identifies a book’s edition, format, and publisher.

Every version of a book requires a separate ISBN. A paperback edition will have a different ISBN from a hardcover, and an audiobook will have another unique ISBN. 

If you’re a self-published author, you can obtain an ISBN through official agencies like Bowker (US) or Nielsen (UK). Some publishing platforms, such as Amazon KDP, offer free ISBNs, but these ISBNs list Amazon as the publisher. 

One crucial advantage of ISBNs is that they make books discoverable beyond Amazon. If you want your book stocked in Barnes & Noble, independent bookstores, or libraries, an ISBN is required.

The ISBN also helps with metadata standardization, meaning bookstores and distributors can correctly classify your book based on title, author, edition, format, and genre. 

Key Differences Between ASIN and ISBN

While both ASINs and ISBNs serve as identifiers, they operate in very different ways. Here’s a direct comparison:

Now let’s discuss things a bit more in detail:

Specificity

One key takeaway is that ASINs are specific to Amazon, while ISBNs are universal across the publishing industry. If you’re only selling on Amazon, an ASIN is all you need. But if you want to sell in bookstores, libraries, or other online platforms, an ISBN is required.

In many cases, a book will have both an ASIN and an ISBN, but they are not the same. A paperback book on Amazon, for example, may have an ISBN that is also used in physical bookstores, but Amazon will still generate a separate ASIN to track it internally.

Requirements

Another important distinction is that Kindle eBooks do not require an ISBN. Amazon assigns an ASIN to all Kindle books, making ISBNs unnecessary unless you plan to distribute your eBook through platforms like Apple Books or Google Play Books, which require ISBNs for cataloging.

ASINs also play a crucial role in Amazon’s private label and FBA (Fulfillment by Amazon) business models. If you sell products beyond books, understanding ASIN management can help you optimize your listings, prevent counterfeits, and improve your product rankings on Amazon’s marketplace.

Relationship Between ASIN and ISBN

While ISBNs and ASINs sometimes overlap, they serve distinct purposes. Amazon uses ISBNs to generate ASINs for books when possible, but the two numbers do not always match. 

For example, an ISBN-13 might be assigned to a book, but Amazon will create an entirely different ASIN that has no correlation with the ISBN.

A common misconception among self-published authors is that an ASIN can replace an ISBN. This is only true if you never plan to sell your book outside Amazon. However, if your book is stocked in libraries, physical bookstores, or multiple online retailers, an ISBN is mandatory.

For authors and publishers using Amazon KDP, if you’re only interested in selling on Amazon, you might opt for the free ISBN provided by KDP. But if you plan to expand your reach, investing in your own ISBN will give you greater flexibility and control.

At ZonHack, we help Amazon sellers and authors navigate Amazon’s complex marketplace, ensuring that their books and products are correctly listed, optimized, and reaching the right audience. Whether you’re launching a new book or looking to improve your Amazon rankings, understanding ASINs and ISBNs is a small but crucial step in maximizing your success.

Other Relevant Product Identifiers

While ASINs and ISBNs are the most relevant identifiers for books and Amazon products, there are several other identification codes used in eCommerce and publishing. Understanding these can help sellers, authors, and businesses streamline their product listings and distribution.

1. UPC (Universal Product Code)

• Used for: Retail products globally
• Format: 12-digit numeric code
• Purpose: Used for scanning at checkout in physical stores
• Relevance to Amazon: Required for many product categories; Amazon may convert UPCs into ASINs

2. EAN (European Article Number)

• Used for: Products outside North America
• Format: 13-digit numeric code
• Purpose: European counterpart of UPC
• Relevance to Amazon: Used in product listings, converted into ASINs for Amazon tracking

3. GTIN (Global Trade Item Number)

• Used for: Identifying products globally
• Format: Can be UPC, EAN, or ISBN
• Purpose: Universal identifier for trade items
• Relevance to Amazon: Helps sellers list products in Amazon’s catalog

4. ISSN (International Standard Serial Number)

• Used for: Periodicals (magazines, journals, newspapers)
• Format: 8-digit numeric code
• Purpose: Identifies serial publications
• Relevance to Amazon: Used for listing magazines and serial publications

Each of these identifiers plays a role in Amazon’s cataloging system and the broader retail and publishing ecosystem. If you’re selling books or products beyond Amazon, understanding these codes ensures smooth distribution and accurate tracking.

Best Practices for Managing ASINs and ISBNs

Managing ASINs and ISBNs correctly ensures better visibility, proper inventory tracking, and compliance with Amazon’s guidelines. Here are the best practices for sellers and publishers:

1. For Self-Published Authors

• If selling exclusively on Amazon, an ASIN is sufficient (especially for Kindle eBooks).
• If planning to sell beyond Amazon, purchase an ISBN to ensure global distribution.
• Consider getting your own ISBN instead of using Amazon’s free ISBN if you want full publishing rights and branding.
• Keep track of different ISBNs for different formats (paperback, hardcover, audiobook, etc.).

2. For Amazon Sellers

• Use Amazon’s ASIN lookup tool to find existing ASINs before creating new listings.
• If selling a product already in Amazon’s catalog, use the existing ASIN to avoid duplicate listings.
• For private label products, obtain UPCs or GTINs before listing, as Amazon requires them.
• Regularly monitor ASIN changes to prevent hijacking or incorrect modifications by unauthorized sellers.

3. For Publishers and Large-Scale Book Distributors

• Maintain a database of ISBNs, ASINs, and GTINs to track different editions and formats.
• Ensure metadata consistency across different marketplaces (Amazon, Barnes & Noble, Apple Books, etc.).
• Use Amazon Advantage or other bulk listing programs to manage large inventories effectively.

Properly managing your product identifiers reduces listing errors, improves search visibility, and ensures accurate tracking across different platforms.

Frequently Asked Questions (FAQs)

1. Can a book have both an ASIN and an ISBN?

Yes. A book listed on Amazon will have an ASIN for Amazon’s system, but if it has an ISBN, Amazon will often associate the two. However, Kindle eBooks only have ASINs since ISBNs are not required for digital formats.

2. Can I sell a book on Amazon without an ISBN?

Yes. If you publish through Amazon KDP, Amazon will assign your book an ASIN even if you don’t have an ISBN. However, if you want to sell your book outside of Amazon (e.g., Barnes & Noble, Apple Books, IngramSpark), an ISBN is required.

3. How do I get an ISBN for my book?

• Bowker (US) – https://www.myidentifiers.com
• Nielsen (UK) – https://www.nielsenisbnstore.com
• International agencies – Check the ISBN International website: https://www.isbn-international.org

You can purchase an ISBN from an official ISBN agency, such as:

4. Does Amazon provide free ISBNs?

Yes, but only for print books through KDP. If you accept Amazon’s free ISBN, Amazon will be listed as the publisher, and you cannot use that ISBN to sell the book outside of Amazon.

5. Can I reuse an ISBN for a new edition of my book?

No. Each edition (paperback, hardcover, revised edition) must have a unique ISBN.

6. Can I change an ASIN for a product on Amazon?

No. ASINs are permanent once assigned. If a listing needs changes (e.g., title, description, or images), you must edit the existing listing rather than request a new ASIN.

7. How do I find an ASIN on Amazon?

You can find the ASIN:

• In the product URL (e.g., https://www.amazon.com/dp/B09XYZ1234 – the ASIN is B09XYZ1234)
• On the product details page under “Product Information”
• Using Amazon’s ASIN lookup tools or third-party tools like Helium 10, Jungle Scout, or AMZScout

ASIN vs. ISBN – Which One Do You Need?

The choice between an ASIN and an ISBN depends on where and how you plan to sell your book:

• If you’re selling only on Amazon, an ASIN is sufficient.
• If you want to sell in bookstores, libraries, or other retailers, you need an ISBN.
• Kindle eBooks do not require an ISBN, only an ASIN.
• Printed books (paperback, hardcover) can have both an ASIN and an ISBN.

For Amazon sellers, ASINs are essential for product tracking and SEO, while for publishers and authors, ISBNs ensure broader distribution. Understanding these identifiers helps optimize sales, improve visibility, and expand reach beyond Amazon.

At ZonHack, we help authors, publishers, and sellers optimize their Amazon listings, manage ASINs, and improve product visibility. Whether you’re launching a new book, selling private-label products, or expanding your business, our expertise can help you succeed.

Need help optimizing your Amazon listings or book sales? Contact us today!