EPUB Metadata Checker
Upload an .epub file to see whether its metadata meets the EPUB spec's requirements before you submit it to a storefront.
Frequently asked questions
- What does this tool actually check?
- It reads your EPUB's package document (content.opf) and checks the elements the EPUB 2/3 spec requires: dc:identifier, dc:title, dc:language, and — for EPUB 3 files only — a dcterms:modified timestamp. It also checks that the package's unique-identifier attribute correctly points at one of your dc:identifier elements, and whether a cover image is declared and actually present in the file.
- Is my book file uploaded anywhere?
- No. The EPUB is read and parsed entirely in your browser using JavaScript — it's never sent to a server. You can check this yourself in your browser's network tab.
- Why does it flag my language code as a warning instead of an error?
- The checker verifies your language code has the right shape for a BCP 47 tag (like "en" or "en-US") but doesn't look it up against the full IANA language subtag registry, so an oddly-shaped-but-technically-valid tag might get flagged, and an invalid-but-shape-correct one might not. Treat it as a heads-up, not a definitive pass/fail.