Do You Need an ISBN for KDP?
Short answer: it depends on the format. Here's exactly when you need one, when Amazon gives you one free, and when buying your own is worth it.
| Format | ISBN needed? |
|---|---|
| Kindle eBook | No, eBooks don't use ISBNs on Amazon at all |
| Paperback | Yes, either a free KDP one or your own |
| Hardcover | Yes, needs its own separate ISBN from the paperback |
Free KDP ISBN vs. your own
If you don't provide one, Amazon assigns a free ISBN automatically when you publish a paperback. That's genuinely fine for most self-publishers. The tradeoff: it lists Amazon as the publisher of record, and it can only be used for that exact edition on Amazon, you can't take it to another retailer or print service.
Buying your own ISBN lists you as the publisher and can follow the book to other retailers, formats, or print services if you ever expand beyond Amazon. In the US, ISBNs are purchased through Bowker (myidentifiers.com), the official US ISBN agency. Other countries have their own national agencies.
Common questions
Do I need an ISBN to publish on KDP?
Kindle eBooks don't need one at all. Paperbacks need one, but Amazon provides a free one automatically if you don't supply your own.
What's the difference between a free KDP ISBN and my own?
A free one lists Amazon as publisher and only works for that edition on Amazon. Your own lists you as publisher and can be used across other retailers and formats.
Can I use the same ISBN for paperback and hardcover?
No. Each format and edition needs its own unique ISBN.
Where do I buy my own ISBN?
In the US, through Bowker (myidentifiers.com). Other countries have their own national ISBN agencies.
Why this matters
Most publishers starting out don't need to spend money on ISBNs, the free KDP one covers Amazon-only publishing just fine. It's really only worth buying your own once you're planning to sell through other retailers too.
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