Is the EPUB checker free?

Repair and the browser-side pre-publish checks are free and need no account. A limited trial of official EPUBCheck and Ace by DAISY runs comes with a free account, because those run on a server.

What does Ace by DAISY check?

Ace reports machine-checkable accessibility problems such as missing alternative text, invalid ARIA roles and missing document semantics. It does not replace manual accessibility review.

Opening and repairing a book happens entirely in your browser. Only the official EPUBCheck and Ace runs send the exported file to a server, and only when you ask for a report.

Check an EPUB — and get it back repaired.

Drop a book to see what is wrong with it. Invalid markup, missing navigation and broken accessibility roles are corrected as it opens, and what is left is listed so you can fix it here.

Broken markup, navigation and roles repaired as it opens
Findings you can act on, not just a list
Repair runs in your browser, with no account
Official validation with a free account — EPUBCheck and Ace by DAISY

Drop an EPUB here

.epub — up to 90 MB

Browse file

EPUB only90 MB maxBrowser-only

How it works

Drop an EPUB

Up to 90 MB. Nothing is uploaded to open it.

See what was repaired

Counts by category, then what changed in each chapter.

Fix the rest and check it

Edit here, then run EPUBCheck and Ace against the exported file.

What is corrected, and what is only reported.

Repaired for you

Invalid markup, missing namespaces, illegal URLs and unusable ARIA roles are corrected while the book opens.

Navigation rebuilt

A missing or unreadable table of contents is recovered from the book's own files.

Accessibility filled in

Roles the semantics already imply are added, so assistive technology is told what the book means.

Official checks

EPUBCheck and Ace by DAISY run against the exported file and report with their own versions.

Don't have an EPUB yet?

Convert your existing documents first — then check the result here.

PDF to EPUB Markdown to EPUB DOCX to EPUB