What Is an ASIN? Amazon's Book ID Explained for Authors

An ASIN (Amazon Standard Identification Number) is a 10-character code Amazon assigns to every product in its catalog, including every edition of your book. It identifies your book only inside Amazon's stores. It is not a replacement for an ISBN, which is recognized by bookstores, libraries and distributors worldwide.

If you publish a Kindle ebook through Amazon KDP, you get an ASIN automatically and for free. You do not apply for one, buy one, or choose it. The rest of this guide covers how ASINs differ from ISBNs, where to find yours, and why your ebook and paperback end up with different numbers.

What an ASIN looks like

An ASIN is 10 characters long and can contain both letters and numbers. Two patterns are common for books:

• Kindle ebooks usually get an ASIN that starts with "B0", followed by eight more letters and digits. Something like B0XXXXXXXX.
• Print books (paperbacks and hardcovers) often use the book's 10-digit ISBN as the ASIN, when the book has one. So a paperback's ASIN may look like a string of digits rather than starting with "B".

You will see the ASIN in the "Product details" section of an Amazon book page, and in the page's web address. On a typical Amazon product URL, the ASIN is the 10-character code that appears right after /dp/.

For a short definition you can bookmark, see the ASIN glossary entry.

How an ASIN differs from an ISBN

Both are identifiers, but they do different jobs.

An ISBN (International Standard Book Number) is a global book identifier. It is issued by the official ISBN agency in your country (or by a publishing platform that assigns one on your behalf). Bookstores, libraries, wholesalers and distributors use it to order, catalog and track a specific edition of a book. Modern ISBNs have 13 digits. You can read more in the ISBN glossary entry.

An ASIN is Amazon's internal product code. It exists so Amazon can track every item it sells, from books to kitchen gadgets. Outside Amazon, an ASIN means nothing. Apple Books, Kobo and libraries cannot use it to find your book.

	ASIN	ISBN
Full name	Amazon Standard Identification Number	International Standard Book Number
Who issues it	Amazon, automatically	Your national ISBN agency, or a platform that assigns one
Where it works	Amazon stores only	Bookstores, libraries, distributors worldwide
Length	10 characters, letters and numbers	13 digits (older format: 10 digits)
Cost	Free	Varies by country; some platforms give free ones with restrictions
Needed for a Kindle ebook?	Assigned automatically	Not required, per KDP's published terms
Needed for a KDP paperback?	Assigned automatically	Required (KDP's free ISBN or your own)
Can you choose it?	No	You choose which of your purchased ISBNs to assign
Transferable to another store?	No	Yes, if you own it

The practical takeaway is that one never replaces the other in places where both matter. A Kindle ebook can live on Amazon with only an ASIN. A paperback on Amazon needs an ISBN, and Amazon will also give it an ASIN for its own catalog.

When you still need an ISBN alongside an ASIN

Whether you need an ISBN depends on the format and where you plan to sell.

According to KDP's published terms, a Kindle ebook does not require an ISBN. Amazon assigns a free ASIN, and that is enough to publish and sell on Amazon. Many self-published authors who sell ebooks only on Amazon never get an ISBN for the ebook at all.

A KDP paperback does require an ISBN. You can use a free ISBN that KDP provides or one you bought yourself. KDP's free ISBN can only be used for distribution through KDP. If you later want to publish the same paperback through IngramSpark, IngramSpark's terms say you need your own ISBN for each format, and a free KDP ISBN can't be used there.

If you sell ebooks on other stores, check each one. Apple Books, Kobo and Google Play Books do not require an ISBN for ebooks under their current published terms. Google assigns its own identifier, called a GGKEY, in a similar way to Amazon's ASIN. Rules can change, so confirm in each store's dashboard before you publish.

For a full walkthrough of when an ISBN is worth buying, read Do I need an ISBN?. If you have a 10-digit ISBN and need the 13-digit version (or the reverse), the ISBN converter handles that.

Where to find your book's ASIN

There are three reliable places to look once your book is live.

1. Your KDP Bookshelf

Sign in to your KDP account and open your Bookshelf. After a book is published, KDP lists the ASIN with each format, near the title and its status. The Kindle ebook and the paperback each show their own identifier. If the book is still "In review", the ASIN may not appear yet.

2. The Amazon product page

Search for your book on Amazon and open its page. Scroll down to the "Product details" section. For a Kindle edition, you will see a line labeled ASIN. For a paperback, you will usually see ISBN-10 and ISBN-13 lines, and the ASIN may match the ISBN-10.

Make sure you are on the right format. Amazon shows format buttons (Kindle, Paperback, Hardcover) near the top of the page. Click each one and the product details, and the ASIN, will change.

3. The page URL

Look at the address bar while on your book's page. Find /dp/ in the URL. The 10 characters right after it are the ASIN for the format you are viewing. This is handy when you need the number quickly to share a clean link or set up an ad.

Why your ebook and paperback have different ASINs

Amazon treats each format as a separate product. The Kindle ebook, the paperback and the hardcover are each a distinct item with its own price, its own file and its own sales record. So each one gets its own ASIN.

Here is how it typically plays out for a single book:

• Kindle ebook: ASIN assigned by Amazon, usually starting with "B0". No ISBN needed.
• Paperback: has an ISBN (from KDP or your own). Its ASIN is often the ISBN-10. If your ISBN starts with 979, there is no 10-digit ISBN version, so Amazon gives the paperback a different ASIN instead.
• Hardcover: a separate ISBN and a separate ASIN again.

Different ASINs do not mean separate product pages for shoppers. Amazon links formats of the same book together so readers see one page with format buttons. When the title, author name and other details match exactly, this linking usually happens on its own within a few days of the second format going live.

How Kindle and paperback ASINs get linked

Format linking depends on your book details matching. Amazon compares the title, subtitle, author or contributor names, and series information across formats. Small differences can stop the link from happening, such as a subtitle on one edition and not the other, a middle initial on one author name, or a different spelling.

If your formats have been live for a few days and are still on separate pages, you can contact KDP support from your account and ask them to link the editions. Give them both ASINs, or the ASIN and the ISBN. It helps to have the identifiers ready before you reach out.

Keeping your metadata consistent from the start avoids most of this. Write your title, subtitle and author name once and copy them exactly into every format's setup. If you build your book in Inkora, the publishing kit gives you the description, keywords and BISAC categories in one place, and the Publishing Hub has separate step-by-step checklists for KDP ebook and paperback setup, which makes it easier to enter the same details twice. You still upload in your own KDP account.

What authors actually use the ASIN for

Once your book is live, the ASIN comes up more often than you might expect:

• Sharing a clean link. A link built from the ASIN after /dp/ is shorter and tidier than the long URL you get from a search.
• Amazon Ads. When you set up product-targeted ads, you target other books by their ASINs. You may also need your own book's ASIN when creating a campaign.
• Author Central. When you claim your books on your Amazon author page, you can search by title, ISBN or ASIN to find the right editions.
• Support requests. KDP support will usually ask for the ASIN when you report a problem with a listing, a linking issue or a review question.
• Promotions and Kindle programs. Tools inside KDP, such as promotions for books enrolled in KDP Select, refer to your books by format, and the ASIN helps you confirm you are working on the right one.
• Your website and newsletter. Buy buttons and links should point to the right format. Keep a list of each format's ASIN.

ASINs across Amazon countries

For a Kindle ebook, the same ASIN is usually used across Amazon's marketplaces, such as Amazon.com, Amazon.co.uk and Amazon.de. Only the domain in the URL changes. This makes it easy to give readers a link for their own country.

Print editions are more variable because availability depends on where KDP prints and distributes. If a link does not work in a particular marketplace, check that the format is actually available there in your KDP settings and on that store's site.

Common problems and fixes

"My Bookshelf doesn't show an ASIN." The book is probably still in review or has not finished publishing. KDP review can take up to a few days. Once the status changes to "Live", the ASIN should appear. If the book is live on Amazon but the number still isn't showing in your Bookshelf, find it on the product page under "Product details" or in the URL.

"My paperback ASIN is just numbers. Is something wrong?" No. Print books often use the ISBN-10 as their ASIN. That's normal.

"My ebook and paperback are on separate pages." Wait a few days after the second format goes live. If they are still separate, compare the title, subtitle, series name and author name across both formats character by character. Fix any mismatch, or contact KDP support with both identifiers and ask them to link the editions.

"I want to change my ASIN." You can't. Amazon assigns it and it stays with that product. If you publish a genuinely new edition as a new title, it gets a new ASIN, and reviews and sales history may not carry over the way you expect. Before republishing, read KDP's current guidance on what counts as a new edition versus an update to an existing book. Many changes, like fixing typos or uploading a new cover, can be made to the existing book without creating a new ASIN.

"I unpublished my book and it still shows on Amazon." Unpublishing stops new sales, but the product page may remain, often marked as unavailable, so past buyers and reviews still have a home. The ASIN does not get freed up for reuse. If you republish the same book from your Bookshelf, it normally returns under its original ASIN.

"I used my Kindle ASIN on another store's form." Other stores can't use an ASIN. Leave the identifier field blank if the store assigns its own, or enter an ISBN if you have one for that format. Never reuse a paperback ISBN for an ebook, or one format's ISBN for another.

"I gave KDP the wrong ISBN for my paperback." Once a paperback is published, KDP does not let you change its ISBN. You would need to publish the book again as a new paperback with the correct ISBN, which also means a new ASIN. Double-check your ISBN before you click publish. The guide to publishing a paperback on KDP covers this step.

If you are setting up your first Amazon listing, the Amazon KDP publishing guide walks through each field in order, including where identifiers fit in.

An ASIN is Amazon's own label for each format of your book. You get one for free, you cannot pick or change it, and it never replaces an ISBN outside Amazon. Note down every format's ASIN once your book goes live, keep your details identical across formats, and you will rarely have to think about it again.