ISBN, ISSN and ISMN explained: which number does your book need?
ISBN for books, ISSN for periodicals, ISMN for printed music — what each standard number is, whether self-published authors need an ISBN, free versus paid, one number per format, and where to buy them by country.
Most self-published authors need an ISBN — the standard identifier for books. An ISSN is for periodicals and ongoing series; an ISMN is for printed sheet music. If you are publishing a standalone book, ISBN is the number you want. You do not strictly need one to sell an eBook on Amazon, but you do for almost everything else.
What is the difference between an ISBN, an ISSN and an ISMN?
All three are international standard numbers, run by separate but related agencies, and each identifies a different kind of publication. Confusing them is common, so here is the plain version, side by side.
| Number | Stands for | Identifies | Length | Example use |
|---|---|---|---|---|
| ISBN | International Standard Book Number | A single book, or one specific edition or format of it | 13 digits | Your novel, your memoir, your non-fiction title |
| ISSN | International Standard Serial Number | A serial — a publication that continues indefinitely | 8 digits | A magazine, a journal, a numbered book series as a whole |
| ISMN | International Standard Music Number | Printed, notated music | 13 digits, begins 979-0 | A score, a songbook, sheet music |
The short rule: a book gets an ISBN. A thing that keeps coming out — issue after issue, volume after volume — gets an ISSN. Notated music gets an ISMN. A poetry collection, a cookbook, a children’s picture book and a thriller are all simply books, so they all take ISBNs.
The overlapping cases
A book series is where people tie themselves in knots. Each book in a series still gets its own ISBN; the series as a whole can additionally carry an ISSN, the way a magazine title does, but that ISSN never replaces the per-book ISBNs. A songbook is the genuinely ambiguous one: if it is mainly notated music it can take an ISMN, and many music publishers give such titles both an ISMN and an ISBN so the trade can shelve them like books.
Do self-published authors actually need an ISBN?
It depends on where and how you are selling, and this is the question that matters most, so here is the honest answer rather than a blanket yes.
- eBook on Amazon Kindle only: no ISBN required. Amazon assigns its own internal identifier (an ASIN), and your eBook will sell perfectly well without an ISBN.
- Print book, anywhere: effectively yes. Every print retailer, distributor, library and wholesaler keys off the ISBN. Without one your printed book is close to invisible to the trade.
- eBook in any wider store — Apple Books, Kobo, Google Play, library platforms: usually yes, or strongly recommended. Some accept titles without one; most expect it, and an ISBN makes your book traceable everywhere at once.
So if you are doing anything beyond a Kindle-exclusive eBook, you want an ISBN. It is the spine of your book’s identity in every catalogue on earth.
Do you need a separate ISBN for each format?
Yes — and this trips up nearly every first-time author. One ISBN identifies one format of one edition. The paperback, the hardcover and the eBook are three different products, so they need three different ISBNs, even though it is the same book by the same author.
An ISBN points to something a shop can stock and a reader can buy as a distinct thing. Change the binding or the file type, and you have changed the product. A reflowable ePUB and a Kindle file usually count as the same eBook format and can share one ISBN, but a paperback and a hardcover never share.
You do not need a new ISBN for a reprint, a corrected typo or a new cover that leaves the text essentially unchanged. You do need one for a genuinely new edition — substantially revised or expanded. If in doubt: same content and format means same ISBN; new content or new format means new ISBN.
| What you are publishing | ISBNs needed |
|---|---|
| Paperback only | 1 |
| Paperback + eBook | 2 |
| Paperback + hardcover + eBook | 3 |
| A new, substantially revised edition of any of the above | 1 more per format |
| A reprint with a fixed typo | 0 — reuse the existing ISBN |
This is why authors planning several formats often buy a small block of ISBNs at once: a block is far cheaper per number, and you will use them.
Free ISBN or paid ISBN — what is the trade-off?
You will be offered a free ISBN, most visibly by Amazon’s KDP for print books. It is genuinely free and it works — but it is not really yours, and that distinction has consequences worth understanding before you accept it.
A free KDP ISBN lists Amazon (an Amazon imprint) as the publisher of record, not you or your own imprint name. It is generally tied to printing through that platform, so it does not travel cleanly to another printer. It is fine if you only ever intend to publish that one book, through that one channel, and you do not care whose name sits in the publisher field.
A paid ISBN you buy yourself from your national agency lists you (or your imprint) as the publisher. It is portable — the same ISBN follows your book to any printer, distributor or store — and keeps you in control of your own metadata. The cost is the catch: a single number can be expensive, which is why blocks exist and why the per-number price drops sharply when you buy ten or a hundred.
The rule of thumb: if this is a one-off Kindle-and-KDP-print hobby title, the free ISBN is fine. If you are building an author brand or an imprint and may move between printers and stores, buy your own — being the publisher of record on your own book is worth the price.
Where do you buy an ISBN, by country?
ISBNs are issued nationally. You buy from the agency for the country where you, the publisher, are based — not the country where the book is printed. The global coordinating body is the International ISBN Agency, and it lists the correct agency for every territory. A few you are likely to need:
- United States: Bowker (MyIdentifiers) is the sole official source — and the reason US authors are quoted such high single-ISBN prices.
- United Kingdom & Ireland: Nielsen.
- Canada: Library and Archives Canada — free to Canadian publishers.
- Serbia: the National Library of Serbia, which administers ISBN, ISSN and ISMN for the country.
- Most of the EU: the national library or a designated national ISBN agency, often at modest cost or free.
Prices and policies vary wildly between countries — some national agencies issue ISBNs free to resident publishers, others charge per number — so always start from your own national agency rather than a reseller. ISSNs are issued by the ISSN Network through national centres, and ISMNs through the national ISMN agencies, on the same country-based model.
The shortcut: which number do I need?
If you are preparing a book — fiction, non-fiction, poetry, a children’s title — you need an ISBN, one per format, and you should weigh a free platform ISBN against buying your own. You only reach for an ISSN if you are launching something serial, and an ISMN only for notated music. For most self-publishers the answer is simply: ISBN, and as many as you have formats.
Getting the numbers right is the easy part; getting files that actually pass a store or printer’s checks on the first attempt is where most launches stall. With over 15 years in publishing, we build press-ready print files and validated ePUBs that upload cleanly the first time, with your ISBN and metadata set correctly per format — and a fixed quote upfront. If you would rather hand the technical side over, tell us what you are publishing.
Frequently asked questions
Should I use Amazon’s free KDP ISBN or buy my own?+
KDP’s free ISBN works, but it’s tied to Amazon’s print distribution — you can’t reuse that number anywhere else, and KDP is listed as the publisher of record. If you want your own imprint named and the freedom to print or distribute the same edition elsewhere, buy your own ISBN. For a Kindle-only eBook you need no ISBN at all.
Where do I get an ISBN and how much does it cost?+
ISBNs come from the official agency for your country — for example Nielsen in the UK, Bowker in the US, and a national library or agency elsewhere. Prices and rules vary widely by country, and some agencies issue them free while others sell them singly or in blocks. Check your national ISBN agency directly for current pricing, as it changes and differs everywhere.
Who is listed as the publisher on a self-published book’s ISBN?+
Whoever registers the ISBN is recorded as the publisher of record. If you buy your own ISBN, you can register your own name or imprint — so you stay the publisher and keep all rights. A free retailer-supplied ISBN typically names that retailer instead. With Librum you still register and own the ISBN yourself, so your imprint stays on the record.
Do I need a new ISBN for a second edition or a revised version?+
A significant revision — new content, a changed title, or a different edition — needs its own ISBN, because it’s effectively a new product. Minor fixes such as correcting typos usually don’t. Rules can be interpreted differently, so when you’re unsure, check your national ISBN agency’s guidance. Note that a new cover alone generally doesn’t require a new ISBN, though a format change always does.