EPUB Validate & Repair — Check Any E-book Against the EPUB Standard
Drop an EPUB e-book and get a clear, severity-grouped report: errors that break reading, warnings strict readers may reject, and notes. When the only problems are packaging deviations, download a repaired copy — all locally, nothing uploaded.
Why validate your EPUB e-books
Spec-Based Structure Checks
Validates the package against the EPUB standard: the mimetype entry (first, uncompressed), META-INF/container.xml bootstrapping, the OPF package document, manifest, spine and content types.
Clear Errors, Warnings & Notes
Every finding is graded by severity with a plain-language explanation — red for things that break reading, amber for deviations most readers tolerate, gray for observations.
Chapter & File Integrity
Confirms every manifest and spine entry actually exists in the archive and that each chapter's content is well-formed XML that strict readers can open.
Metadata & Navigation Review
Flags missing title, language, author and unique identifier, and tells you whether the e-book ships a proper EPUB3 navigation document or EPUB2 NCX table of contents.
One-Click Repair Download
When the only problems are mimetype packaging deviations — the most common real-world violation — download a corrected copy with the mimetype file first and uncompressed.
100% Local & Private
Validation runs entirely in your browser with no upload, no server and no sign-up. Your e-books never leave your device.
What EPUB validation does
An EPUB is a ZIP container with a strict set of structural rules. This validator checks those rules in order: the mimetype file must be the first entry and stored uncompressed, META-INF/container.xml must bootstrap the package, the OPF package document must declare metadata, a manifest and a reading order (spine), every referenced file must actually exist, and each chapter must be well-formed XML. The result is a report that separates real problems (errors) from tolerated deviations (warnings) and observations (notes), so you know exactly which issues will break readers and which are harmless.
How to use the EPUB validator
Three steps — validation is automatic once your file is dropped.
Drop your EPUB
Drag and drop an .epub e-book onto the upload area, or click to browse. Validation starts immediately — no button needed.
Read the report
Findings are grouped by severity. Errors break reading, warnings are spec deviations most readers still tolerate, and notes are useful observations like a missing cover or orphan files.
Fix and download
If only the mimetype packaging is wrong, download a repaired EPUB. Otherwise use the report to fix the e-book in an editor, or download the report as a text file for reference.
Important notes
This validator checks the EPUB package structure and content — it does not render the book or check visual layout, and it cannot detect DRM or encrypted content. Warnings like an unescaped HTML entity or a missing cover rarely stop modern readers, but they can fail strict validators and some e-readers. The repair option only re-packs the container (mimetype-first, STORED); it never modifies your content files. EPUB2 and EPUB3 packages are both checked.