Apple Books EPUB Checker

This is a pre-flight check for self-publishing authors and small presses preparing an EPUB for Apple Books, whether you upload directly or route the file through an aggregator. It applies the rules Apple publishes: books must pass EPUBCheck, images inside the book must not exceed 5.6 million pixels, and the cover should be marked in the package. Catching those before upload saves a rejection round.

It fits naturally into the last mile of ebook production: you have exported an EPUB from your authoring tool and want a second opinion before submission. It also helps when a previous Apple submission bounced and you are trying to narrow down which field or file was at fault. Because it reports per-check detail, it doubles as a quick metadata audit for a back catalogue you are about to re-distribute.

It only inspects and reports: it does not create, fix or upload EPUBs.

The flow is one step: drop an .epub file onto the dropzone (or pick it through the file dialog), and the check runs immediately in your browser. It expects a real EPUB container. Parsing and all checks happen locally; nothing is uploaded, and closing the tab discards everything. DRM-protected files are detected and refused rather than inspected.

The report covers: the EPUB structure (the checks EPUBCheck most often fails books on, from the mimetype file to well-formed pages), with each problem listed; whether a cover image is marked inside the book; every JPEG, PNG, GIF and WebP image, measured from its file header against Apple's 5.6-million-pixel limit, with any image over it named; the title, language and author; and a note comparing the book's cover with Apple's 1400-pixel minimum for cover art. Each line returns pass, warning, fail or note, and the report can be downloaded with Apple's source pages listed.

Two notes on scope. Apple's cover art is a separate marketing image delivered alongside the book, so this tool cannot check it; it only says whether the cover inside the book is big enough to reuse. And the structure checks are a subset of EPUBCheck, which Apple requires in full.

The biggest pitfall is reading a clean report as approval. This is an unofficial pre-check; Apple's own validation and review can still flag issues this tool never sees, including content policy, fixed-layout and rich-media specifics. Treat a clean result as "no known blockers found", not "approved".

Watch the images. A photo or map exported at print resolution can exceed 5.6 million pixels (3000 × 2000 is 6 million), and one such image is enough to fail. Resize it rather than compressing it, since the limit counts pixels, not bytes. SVG images are not measured, because they have no fixed pixel size.

Other common misses: a title or identifier passes when the field exists, even if the value is wrong, since the tool does not check that an ISBN is valid; and a non-EPUB or damaged file fails to open rather than producing a partial report.

Start with the failures: structure errors, images over the pixel limit, a missing title or language. Then resolve the warnings, such as an unmarked cover or a missing author. Re-run the check after any edit, since the tool only reflects the file you dropped in.

Then check what the tool cannot: confirm your separate cover art is RGB and at least 1400 pixels on the shorter side, read back the title, author, language and identifier values to make sure they are correct and not just present, and page through the book in a real reader to confirm the reading order.

For any official, contractual or revenue-bearing release, run EPUBCheck itself and rely on Apple's own validation during upload, plus a dedicated accessibility tool such as Ace by DAISY if accessibility compliance matters. A clean report here reduces surprises; it does not replace Apple's verification.