EPUBCheck-TS

Free Online EPUB Validator

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What is this tool?

EPUBCheck-TS is a free online EPUB validator that checks your ebook files for errors and compatibility issues. Whether you're an author, publisher, or developer, this tool helps ensure your EPUB files meet the official EPUB specification before publishing.

100% Private - Your Files Stay on Your Computer

Unlike other online validators, your EPUB file is never uploaded to any server. All validation happens entirely in your web browser using WebAssembly technology. Your manuscript, your content, your data - it all stays on your computer. Nothing is transmitted over the internet.

Fast and Instant Results

Get validation results in seconds. No waiting for server processing or queue times. The validator runs locally on your device, so it's as fast as your computer allows.

What does EPUB validation check?

Structure - Verifies the EPUB container format and required files
Metadata - Checks title, author, language, and other book information
Content - Validates XHTML, CSS, and navigation documents
Accessibility - Detects missing alt text, empty links, and other a11y issues
Cross-references - Ensures all internal links and resources are valid

Supported EPUB Versions

This validator supports EPUB 2.0, EPUB 3.0, 3.1, 3.2, and 3.3. It automatically detects the version of your ebook and applies the appropriate validation rules.

Current Limitations

This tool catches most common EPUB errors but doesn't cover everything yet. It currently detects about 65% of the issues that the official EPUBCheck tool would find. For final publishing, we recommend also checking with the official tool if you need comprehensive validation. We're actively improving coverage.

Who is this for?

Authors - Check your ebook before publishing on 3ook.com, Amazon, Apple Books, or Kobo
Publishers - Quality assurance for your publishing workflow
Developers - Test EPUB generation in your applications
Designers - Validate ebook layouts and styling