EPUB Validator
Checks EPUB structure — ZIP layout, container, OPF manifest, and file references. Runs in your browser.
What it checks
Whether mimetype is first and uncompressed with the correct content, whether META-INF/container.xml exists and points to an OPF, whether the OPF manifest lists files that actually exist in the archive, and whether the spine refers to manifest ids. Results are shown by file and severity.
What it does not do
This is a structural validator, not a full EPUBCheck replacement. It does not render pages, evaluate CSS or NCX navigation completeness, or confirm every OCF feature. It is meant to catch the packaging mistakes that break readers quickly.
Privacy
The file is parsed locally in your browser. Nothing is uploaded.