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EPUB File Validator

EPUB File ValidatorW3C / IDPF Check

Validate EPUB eBooks against IDPF & W3C specifications. Detect XML syntax errors, broken links, missing assets, and store compliance issues.

Click to select or drag and drop your EPUB file

Upload any .epub eBook (EPUB 2 or EPUB 3). Our client-side validator inspects the entire container, manifests, XML syntax, internal hyperlinks, and metadata in seconds.

Supports EPUB 2.0.1, 3.0, 3.2, 3.3
100% Private. Your files never leave your computer or browser.W3C EPUB 3 & IDPF EPUB 2 Checker
Guide

Why Validate Your EPUB Files?

Authors, publishers, and digital typesetters frequently encounter rejections when submitting EPUB eBooks to Amazon Kindle Direct Publishing (KDP), Apple Books, Google Play Books, or Kobo. Hidden defects like unclosed XHTML tags, missing manifest declarations, uncompressed mimetype headers, or broken hyperlinks can corrupt eBook formatting or crash e-reader devices.

  • Prevent Retailer Rejections: Detect fatal packaging errors, unmanifested files, and spine discrepancies before uploading your manuscript to Amazon KDP or Apple Books.
  • 100% Client-Side Privacy: Validation runs entirely inside your browser using standard web APIs. Your unpublished manuscript and intellectual property are never uploaded to any external server.
  • Actionable Fix Guides: Instead of cryptic terminal logs, receive clear diagnostic descriptions with exact file paths, line numbers, and step-by-step guidance on how to fix issues in Sigil, Calibre, or code editors.
  • Comprehensive Structural Checks: Inspects OCF container files, mimetype compression, OPF package documents, EPUB 2 NCX and EPUB 3 Navigation documents, embedded fonts, and CSS stylesheets.

How EPUB Validation Works

An EPUB file is an Open Container Format (OCF) ZIP archive containing structured XML/XHTML documents, cascading style sheets, image assets, and package metadata. Our client-side validator unpacks the container structure, verifies the uncompressed mimetype file, parses the Open Packaging Format (OPF) manifest and spine, checks every XHTML document for strict XML well-formedness, and validates internal hyperlink targets and multimedia assets against IDPF and W3C specifications.