It passed EPUBCheck, and still looks wrong on a Kindle. This tool looks for the problems that are valid by the spec but bad for readers — 19 of them. EPUBs from any tool are welcome.
EPUBCheck looks for spec violations. This tool looks for the things that are perfectly valid yet still break on a reader’s device.
Missing vertical-writing settings, single digits that lie on their side — detected from symptoms seen in the wild.
Checks whether phonetic guides reach the reader in a usable form and whether digits face the same way as the text around them.
No cover on the shelf, a table of contents that goes nowhere, an empty author field — the things readers notice first.
It does not have to be made with EPUB FACTORY. Any .epub file on your device can be loaded.
The whole analysis runs in your browser. We hold other people’s manuscripts here, so this rule is even stricter than on the conversion side.
Drop a .epub file or choose one. Nothing is uploaded.
The file is opened in your browser. The tool first works out what kind of book it is — vertical or horizontal, text or images — and then applies only the checks that fit.
For every finding you get where it is, what readers will experience, and how to fix it. Results can be exported as text.
This feature handles other people’s manuscripts, which is exactly why we hold the line even harder here than on the conversion side.
Want to build an EPUB from images instead? See Convert images to EPUB — and you can run the result straight through this checker.