Inspect EPUB files 100% locally for Amazon KDP compliance: OPF container, table of contents (NCX/NAV), cover resolution, and formatting issues.
Überprüft mimetype, OPF-Paket, Inhaltsverzeichnis (NCX/NAV), Cover-Auflösung & HTML/CSS-Reflow-Kompatibilität direkt im Browser.
Inspect EPUB files 100% locally for Amazon KDP compliance: OPF container, table of contents (NCX/NAV), cover resolution, and formatting issues.
Drag and drop your completed .epub publication into the validator window or select it via file explorer. The internal package contents and file manifest parse instantaneously.
The validation engine performs an in-depth audit: verifying the OPF package document, inspecting NCX and nav.xhtml navigation trees, validating MIME-type integrity, and parsing XHTML5 syntax.
Examine categorized technical errors and warnings regarding forbidden scripts, broken internal hyper-references, undeclared manifest items, or accessibility gaps.
Ensure your e-book adheres to Amazon KDP ingestion requirements including reflowable responsiveness, fixed-layout metadata, RGB cover resolution, and E-Ink typography.
Apply automated structural fixes or update highlighted code sections and download your certified EPUB ready for seamless publication on Amazon KDP.
GDPR compliant processing • Strict browser privacy • Secure European server hosting
An EPUB 3.3 e-book is not a single file format, but an encapsulated web ecosystem packaged inside a ZIP archive. At the foundation of the e-book lies the Open Packaging Format (OPF) document, which acts as the master manifest. It inventories every XHTML text chapter, CSS stylesheet, embedded font, and visual image. The Spine element dictates the linear reading flow of chapters. In EPUB 3.3, navigation is driven by a semantic HTML5 file (nav.xhtml), which is interpreted by screen readers and reading software to build dynamic tables of contents and landmark menus. If even one file is declared in the manifest but missing from the archive—or conversely, if unmanifested orphan files reside inside the container—the e-book is deemed invalid. Our validator parses every XML node, namespace declaration, and schema constraint to guarantee perfect structural integrity.
Uploading an EPUB to Amazon KDP triggers an automated cloud conversion pipeline that converts the source into Amazon’s proprietary formats, primarily KFX (featuring Enhanced Typesetting) and legacy KF8 (AZW3). Generic EPUB validators often miss Kindle-specific pitfalls. For instance, Amazon strongly expects both modern EPUB 3 nav.xhtml and backward-compatible EPUB 2 toc.ncx to ensure consistent navigation across decades of legacy Kindle hardware. Furthermore, Amazon’s ingestion system strictly flags uppercase characters or special symbols in internal file paths. Hardcoding font sizes in absolute pixels disables Enhanced Typesetting features such as hyphenation, drop caps, and kerning pairs. Our validator replicates these KDP ingestion checks, flagging hidden incompatibilities before you initiate publishing.
Choosing between Reflowable and Fixed Layout (FXL) dictates how your e-book responds to different reading environments. For novels, narrative non-fiction, and poetry, Reflowable Layout is the gold standard, granting readers full autonomy to adjust font size, margins, and background lighting. To support this fluidity, CSS stylesheets must avoid fixed pixel heights or rigid container widths that cause overlapping text blocks on smaller screens. Images must be engineered using responsive percentages (`max-width: 100%; height: auto;`). In contrast, children picture books, graphic novels, and complex technical manuals require Fixed Layout (FXL). This demands explicit OPF metadata declarations, such as `rendition:layout = pre-paginated` and strict viewport coordinates. Our validator audits your CSS and metadata to prevent rendering defects on both E-Ink paper displays and high-resolution tablet screens.
With the enforcement of the European Accessibility Act (EAA) and global publishing mandates, digital accessibility is now a vital publishing requirement. EPUB 3.3 provides powerful semantic tools to empower readers with visual impairments. Incorporating WAI-ARIA roles (`role="doc-chapter"`, `role="doc-footnote"`) and structural HTML5 elements allows assistive text-to-speech engines to navigate footnotes, sidebars, and subheadings effortlessly. Missing descriptive alternative text on critical graphics or language mismatches (`xml:lang`) between chapter files directly impair accessibility. Our validator inspects accessibility declarations across the entire file package. Because the entire auditing process runs strictly on-device inside your browser using WebAssembly, your valuable literary works and unreleased commercial manuscripts remain 100% private.
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