EPUB Accessibility Checker

This is a first-pass accessibility screen for anyone shipping a reflowable EPUB: a self-publisher preparing a title for a store, an editor handing files to a library or institutional distributor, or a developer who just ran a conversion and wants to confirm nothing structural broke. It targets the gaps that most often block screen-reader use — images with no alt attribute, a missing language declaration, no table of contents, an empty reading order — so you can catch them before a distributor's intake check or an end reader does.

It pairs naturally with the EPUB Validator and EPUB Inspector. Validate the file's structure first, use this checker to surface accessibility-specific issues, then open the Inspector if you need to see exactly which content file an image or heading lives in. For students and admins submitting coursework or reports as EPUB, it is a quick way to confirm the book is navigable and language-tagged before it goes into a shared collection.

It is not a publishing gate or a certification. Treat the output as a checklist that tells you where to look, not a stamp that says the book is compliant.

Drop or select a single .epub file. Everything runs locally in your browser — the file is parsed in memory, nothing is uploaded, and closing the tab discards it. DRM-protected files are detected and refused, since assistive technology cannot read them and the tool will not attempt to.

The checker unpacks the EPUB and runs grouped checks: Metadata (title, language, author), Navigation (an EPUB 3 nav.xhtml and a table of contents via nav or NCX), Structure (correct mimetype, a non-empty spine for linear reading order, DRM status, and file size), and Media (it parses each spine HTML file and counts img tags missing an alt attribute). Each result is marked pass, warning, or fail with a short explanation, and a summary tallies the three counts. You can download the whole thing as a plain-text report stamped with the filename and date.

What it does not do: it does not check color contrast (not derivable from EPUB source), does not judge whether existing alt text is meaningful, does not parse heading levels beyond what the listed checks cover, and does not verify full WCAG 2.1 or EPUB Accessibility 1.1 conformance.

The biggest trap is reading a clean alt-text result as 'images are described.' The check only confirms an alt attribute exists on each img tag in the spine — an empty alt="" or a useless value like alt="image1" still passes. It also only inspects img tags inside spine content, so images referenced by CSS, SVG, or files outside the reading order are not counted.

A 'No critical issues' summary means no failures among these specific basic checks, not that the book is accessible. Warnings (a missing nav.xhtml when only an NCX is present, a large file, a missing author) are easy to dismiss but often matter for distributors that require EPUB 3 navigation. Also remember this tool checks one EPUB at a time and only the .epub format — it will not open MOBI, AZW, or PDF.

Open the downloaded report and confirm the failures first: a present and correct title, a declared dc:language, a working table of contents, a non-empty spine, and a valid mimetype. Then revisit every warning rather than skipping it, and for any image flagged as missing alt, open the actual content to write a description that conveys the image's purpose — not just to add an empty attribute that satisfies the count.

Because this is a basic automated screen, re-run it after each fix so you can see counts move, and treat a passing media check as a prompt to manually review alt-text quality yourself. For anything going to a library, an institutional collection, or a market with legal accessibility requirements, run a full audit with Ace by DAISY and have a human verify navigation and reading order before release; do not rely on this checker alone as evidence of compliance for official, contractual, or legally regulated distribution.