Free toolEPUB checker
Before a shop accepts your book it runs a handful of checks. This runs the same ones — and shows you the book on a phone and a tablet, so you can see what your readers will see. Drop your EPUB in and know where you stand in seconds, instead of a week into review.
Your book never leaves your devicenothing is sentnothing is keptYour book stays yours
Your manuscript is the one file you can't afford to have wandering off — so we never ask you to hand it over. The checking and the reading both happen right here, on your own computer.
What it looks at
Around fifteen checks, grouped the way the results are: whether the file opens at all; whether the list of contents inside it is complete and in the right order; whether there's a working table of contents; whether every chapter, link and picture it mentions is actually there; whether the title, author and language are filled in; whether a cover is set; whether the book arrived locked with copy protection (shops add their own and reject books that turn up already locked); and how heavy the pictures are, because Amazon charges about 10p per megabyte to deliver your book and takes it out of your royalty.
What it doesn't
This is the practical once-over, not a line-by-line audit of the ebook standard — it catches what gets books turned away, not every technical detail. If you want the exhaustive version, the W3C's epubcheck is the reference tool. And if what you have is a Word document rather than an EPUB, the DOCX to EPUB converter makes one that passes these checks from the start.
The problems it catches, explained
An EPUB with no table of contents is the single most common reason a book bounces back from review. Readers open the contents menu and find it empty, so shops refuse the file outright. It usually happens when an export tool skips the navigation file — re-exporting from your writing app, or converting the original manuscript again, normally puts it back.
Missing files and broken pictures come from books that were unzipped, edited by hand and zipped back up: the book's own list still mentions a chapter or an image that never made it back into the file. Readers show blank pages or the broken-image icon exactly where your reader shouldn't see one. The checker names the missing files so you know what to restore.
An EPUB rejected for DRM confuses a lot of authors, because the protection was added by the store they bought their own file back from. Shops lock books at the moment of sale — a file that arrives already locked can't be re-locked, so it's turned away. The fix is never to strip anything: export a clean copy from wherever the book was written. Scrambled fonts, by contrast, are normal — the checker tells those two apart so you don't chase a non-problem.
Blank title or author fields don't stop a book opening, which is why they slip through: the file works on your machine, then the store's upload form arrives empty and libraries file the book under “Unknown”. And oversized pictures cost money rather than errors — on Amazon's 70% plan, delivery is charged by the megabyte on every single sale, so a handful of heavy images quietly taxes your royalty forever. The checker weighs each one so you can shrink the right files once.
Keep going: EPUB vs DOCX, explained · how to self-publish a book · all free tools — or skip the file wrangling entirely: publish on Ebokio and the editor exports a clean EPUB for you.