KDP’s submission requirements, recommended formats and screens change from time to time. This article sets out how to think about it; always confirm specific numbers and steps in Amazon’s official help.
This is the single most important thing to know about KDP.
Amazon uses its own file format. You can submit an EPUB to KDP, but on the way in it is converted to Amazon’s own format. What readers actually read is the converted file.
Two things follow from that.
An EPUB with zero validation errors can still display differently from what you intended on Kindle. Correctness as an EPUB and appearance on Kindle have to be checked separately.
In broad strokes, it goes like this.
For vertical Japanese text, check that the required settings are present.
A separate image file for the cover is required.
Use Kindle Previewer, which Amazon distributes free of charge.
Enter the bibliographic details and upload the book file and the cover.
After uploading, check the display in KDP’s own preview as well.
After review, it goes on sale within a day or two.
Of these, step 3 is the one people skip — and it is the step that prevents the most accidents.
To publish a vertically set book on Kindle, an Amazon-specific setting is required.
Without it, the text is vertical in other readers but horizontal on Kindle alone. Pages turn from right to left while the text runs across — an odd, half-finished state.
You also need the page-progression direction and the CSS setting to match. Both are covered below in the checklist.
The title inside the EPUB (dc:title) is the name shown on the shelf in reading apps. Not the file name. If it is empty, the book shows up as "Untitled".
You also type a title into KDP’s registration screen, but it is safer to keep it identical to the one inside the file.
The cover image is prepared separately from the book. KDP does offer a cover creator, but you can also upload an image you made yourself.
There are requirements for recommended resolution and aspect ratio, so check the official help for the current ones.
Kindle Previewer is the checking tool Amazon distributes free of charge. It shows you in advance how your file will look on actual Kindle devices.
| Kind | What to look at |
|---|---|
| Vertically set books | Is it actually vertical |
| Does pressing the left side move you forward | |
| Are the ruby annotations in the right place | |
| Are digits lying on their side | |
| Image-based books | Is the page order right |
| Is the turning direction right | |
| Are images cropped, or are there unexpected margins | |
| Both | Can you jump to each chapter from the table of contents |
| Does the cover display correctly |
Kindle Previewer sometimes holds on to information about a file it has already loaded. If you made a change and nothing moved, try renaming the file and loading it again.
As above, Kindle converts before it delivers. Checking in Apple Books or a desktop EPUB reader tells you nothing about how Kindle will look. Use Kindle Previewer, every time.
That is probably not a file-format problem but a review of your registration details or content. In that case, read what Amazon sent you and follow the instructions.
Kindle Previewer can simulate several devices, but it does not match a real device exactly. If you can, buy your own book after publishing and check it on a real device.
You can replace the file after publishing. It takes time to propagate, and readers who already bought it may not be updated automatically. If a big correction is likely, being thorough before publishing is less work in the end.
Most of what goes wrong with KDP submissions traces back to not knowing that Kindle converts your file. Hold on to that one fact, make Kindle Previewer a habit, and you will avoid most of the serious accidents.
EPUB FACTORY writes every setting a vertically set book needs. Check the file you get in Kindle Previewer before you submit it.
Try EPUB FACTORY