ISBN vs ASIN: What's the Difference for Amazon Authors?

If you’re publishing on Amazon KDP, you’ve likely encountered two different book identifiers: ISBN and ASIN. These two codes serve similar purposes, identifying your book, but they work in completely different ways and have very different implications for your publishing journey.

Let me break this down for you.

What is an ASIN?

ASIN stands for Amazon Standard Identification Number. It’s a 10-character alphanumeric code that Amazon assigns to every single product listed on their marketplace. And I mean every product, not just books. That toaster, those running shoes, and your novel all get ASINs.

Here’s what you need to know about ASINs:

Automatically generated, when your book listing goes live on Amazon
Completely free, Amazon assigns it at no cost
Cannot be changed or customized once assigned
Only works within Amazon’s ecosystem, useless outside of it
Applies to all Amazon products, not specifically books

Think of an ASIN as Amazon’s internal tracking number for their warehouse and catalog system. It helps Amazon organize millions of products across their platform. When someone searches for your book on Amazon, the ASIN is one of the identifiers Amazon uses to find it.

For Kindle eBooks, the ASIN is often the only identifier your book has, and that’s perfectly fine if you’re publishing exclusively on Amazon.

What is an ISBN?

ISBN stands for International Standard Book Number. Unlike the ASIN, an ISBN is a globally recognized 13-digit identifier specifically designed for books (and book-like products). It’s managed by ISBN agencies in different countries and has been the standard book identifier since 1970.

Here’s what makes ISBNs different:

Obtained before publication,you get your ISBN first, then publish
Works worldwide, bookstores, libraries, and retailers everywhere recognize it
Specific to books, designed specifically for the book industry
You can purchase your own, giving you control as the publisher of record
Different ISBN required for each format, paperback, hardcover, and eBook each need their own

Unlike the ASIN that’s assigned automatically, you need to actively obtain an ISBN before your book goes to print or distribution. This lets you include it on your copyright page, back cover, and barcode.

ISBN vs ASIN: Key Differences at a Glance

Feature	ASIN	ISBN
Full Name	Amazon Standard Identification Number	International Standard Book Number
Format	10 alphanumeric characters	13 digits
Applies To	All Amazon products	Books only
When Assigned	After listing goes live	Before publication
Cost	Free (automatic)	Free from KDP or purchased
Scope	Amazon only	Global
Can Be Changed?	No	No (but you can republish with new ISBN)
Who Controls It?	Amazon	You (if you buy your own)

When Do You Need Each Identifier?

For Kindle eBooks

Here’s the good news: you don’t need an ISBN for Kindle eBooks sold on Amazon. The ASIN is sufficient for identifying your eBook within Amazon’s system.

However, if your goal is to publish your eBook on multiple stores; Apple Books, Kobo, Barnes & Noble Nook, Google Play Books then having an ISBN for your eBook is a smart move. Many of these platforms either require or strongly prefer ISBNs for their catalogs.

For Print Books (Paperback & Hardcover)

Print books need ISBNs. Amazon KDP will offer you a free ISBN when you publish a paperback or hardcover, but this comes with some considerations I’ll explain below.

The ASIN will still be assigned to your print book listing on Amazon, but the ISBN is what goes on your back cover, inside your book’s copyright page, and into the wider book distribution network.

Amazon KDP’s Free ISBN: Good Enough?

Amazon KDP offers free ISBNs for print books, and for some authors, this works perfectly fine. If your only goal is to sell your book on Amazon and you’re not concerned about wider distribution, the free ISBN can be a practical choice.

But let’s be honest about what comes with it:

Amazon becomes the publisher of record; your book will show “Independently Published” as the imprint
Limited to Amazon’s distribution; you can’t use that ISBN on IngramSpark or other platforms
Signals self-publishing to industry professionals, bookstores and libraries will know

Is there anything wrong with being self-published? Absolutely not. Self-publishing has democratized the book industry and produced countless bestsellers. But because the barrier to entry is low, there are also many low-quality books flooding the market.

This is where perception matters.

Making Your Book Stand Out

If you want your book to signal quality and professionalism, the ISBN is just one piece of the puzzle. Here’s what actually matters:

1. Invest in Professional Cover Design

Your cover is the first thing readers see. A professional, genre-appropriate cover immediately tells readers this book was made with care.

2. Write a Compelling Book Description

Your Amazon description is your sales pitch. Optimize it with relevant keywords, hooks, and clear benefit statements.

3. Polish Your Book’s Interior

Professional formatting, proper typography, and error-free content all contribute to the reading experience.

4. Use Your Own ISBN and Imprint Name

Having your own ISBN with a custom imprint name establishes you as a professional publisher. Instead of “Independently Published,” your book can show your own publishing brand.

5. Optimize Your Book Listing

Use relevant keywords, select the right BISAC categories, and make sure your metadata is complete and accurate.

6. Get Book reviews

This is most imporatnt part of singnaling your book as a high quality book. Good numbers of reviews means your book is being read and liked by readers. I recommend doing Advance Reader Copy(ARC) campaign to get reviews for your book.

When all these elements come together, your book signals quality, regardless of whether you’re self-published or traditionally published.

The ASIN Cannot Replace an ISBN

Let me be clear about something: even though ASIN and ISBN both serve as identifiers, an ASIN cannot be used outside of Amazon.

If a bookstore asks for your book’s identifier to order copies, you give them the ISBN, not the ASIN. If a library wants to catalog your book, they need the ISBN. If you want to distribute through IngramSpark, Bookshop.org, or independent bookstores, you need an ISBN.

The ASIN is Amazon’s internal system. The ISBN is the book industry’s universal language.

Should You Purchase Your Own ISBN?

If you’re serious about your publishing journey and want maximum flexibility, I’d recommend getting your own ISBN. Here’s why:

You’re the publisher of record not Amazon
Use it anywhere; Amazon, IngramSpark, Draft2Digital, anywhere
Your imprint name appears as the publisher build your brand
Full control over metadata, you decide how your book is represented
Professional perception, signals investment in your work

At FreeISBN.com, we offer ISBNs for just $39 each, a solid deal if you need one or a few ISBNs. And authors from anywhere in the world can obtain an ISBN through us, regardless of their country.

If you need multiple ISBNs for different formats or future books, purchasing makes even more sense from a cost-per-ISBN perspective.

Quick Decision Guide

Use ASIN only (no ISBN) if:

Publishing a Kindle eBook exclusively on Amazon
No plans for wide distribution

Use Amazon’s free ISBN if:

Publishing print books exclusively on Amazon
Don’t mind “Independently Published” as your imprint
Budget is extremely tight

Purchase your own ISBN if:

Want to distribute beyond Amazon
Building a publishing brand with your own imprint name
Want to appear in library and bookstore systems
Planning multiple books or formats
Want maximum control and professionalism

Final Thoughts

ASIN is Amazon’s internal product code, while ISBN is the book industry’s global standard.

For Kindle eBooks on Amazon, the ASIN is sufficient. For print books, especially if you have any ambitions beyond selling exclusively on Amazon, owning your ISBN gives you flexibility, control, and a more professional image.

The limitations of Amazon’s free ISBN are well-documented, and many successful self-publishers eventually transition to purchasing their own ISBNs as their publishing business grows.

If you’re ready to take control of your publishing journey, get your own ISBN today and establish yourself as the publisher of record for your books.