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File processing runs in your browser. Documents are not uploaded to our servers. The site may download processing engines and send usage or feedback events without file contents.

How we handle your data

Laboratory · On your device

EPUB Checker

Check an EPUB's package structure, metadata, manifest, spine, navigation and XHTML in your browser, and download the findings as a text report. Files stay in your browser.

One EPUB up to 30 MB. This is not the official W3C EPUBCheck: it runs its own structural checks in your browser.

Try an example

Download sample EPUB

The sample book passes every check with no errors or warnings. Delete a file from its ZIP, or break a chapter's XHTML, to see the reported error.

What is checked

The ZIP container and its first, uncompressed mimetype file; META-INF/container.xml; that the package document parses; the required identifier, title and language, and the unique identifier; that every manifest item exists and has a media type; that spine items exist; the EPUB 3 navigation document or the EPUB 2 NCX; that each XHTML file is well-formed; and images, stylesheets and links that are missing or not declared.

It does not validate against the full EPUB schemas, CSS, accessibility metadata or fixed-layout rules, so a clean result here does not guarantee that a store will accept the book. Use the official EPUBCheck before publishing. DRM-encrypted content cannot be inspected.

Engine licenses and source code

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