EPUB Checker
100% private, client-side EPUB 3.3 validation. Detects PKG-006, OPF-030, and Amazon KDP upload blockers before submission.
Select your file here to get started
or drop your file here.
What to expect
Experience fast, secure, and completely private processing directly inside your web browser.
Complete Privacy Protection
Your manuscript is processed entirely in local browser memory using JavaScript, ensuring zero files are uploaded.
Instant Validation Results
Get a comprehensive structural report in seconds, highlighting critical errors, warnings, and auto-repairable issues clearly.
KDP-Focused Error Detection
Specifically tuned to catch the exact errors that cause Amazon Kindle Direct Publishing rejections with accuracy.
How it works
Simply upload your content, adjust your settings, and download the result instantly.
Upload EPUB File
Drag and drop your .epub file or browse from your device. Files up to 50MB are supported.
Instant Structural Analysis
The tool decompresses the archive and scans package XML, manifest entries, and content for strict rules.
Review Detailed Report
Get a comprehensive breakdown of errors, warnings, and auto-repairable issues with clear, plain English text.
Frequently Asked Questions
Get quick answers about supported formats, data privacy, and using this tool.
About This Tool
Validate your EPUB files for Amazon Kindle Direct Publishing, Apple Books, and other platforms with this comprehensive pre-flight inspection tool. Running entirely in your browser, it performs deep structural analysis of ZIP packaging, XML metadata, XHTML content, and manifest wiring to catch critical errors before they cause costly upload rejections. The scanner checks mimetype file ordering, unique identifier binding, duplicate XML IDs, disallowed JavaScript, broken asset references, and navigation document compliance. Each issue is explained in plain English with specific remediation strategies, so you know exactly what to fix and why it matters for KDP ingestion. Unlike online validators that upload your manuscript to remote servers, this tool processes everything locally using JavaScript and WebAssembly. Your intellectual property stays on your device at all times, making it safe for unpublished manuscripts, sensitive non-fiction, and proprietary educational content.
