Ace, by DAISY


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Ace, the Accessibility Checker for EPUB, is a tool developed by the DAISY Consortium to assist with the evaluation of accessibility features of EPUB publications.

What is Ace?

Ace is a tool to run automated accessibility checks for EPUB Publications, in order to assist in the evaluation of conformance to the EPUB Accessibility specification.

It is important to keep in mind that only a limited portion of accessibility checks can be automated, and therefore Ace is just a helper tool to assist in a broader, human-driven, evaluation process.

Under the hood, Ace currently runs the axe engine for automated testing of HTML, developed by the good folks at Deque Systems.

Getting started

  • Install Node.JS (version 6 or higher).
  • Install Ace with npm install @daisy/ace -g

If everything went smoothly, you should now be able to run the ace command in your shell.

A detailed getting started guide is also available on

What’s next?

User and developer documentation is available on Ace’s web site.

You can also review the current work plan by looking at the current milestones defined in the issue tracker.

Who’s using Ace?

Several publishers and service providers have integrated Ace in their production or QA workflows, including:

  • Hachette Livre France
  • Vital Source

Some tools based on Ace are also well worth checking out:

  • BACC – the born accessible content checker – developped by the German Central Library for the Blind in Leipzig (DZB). It is a web application backed by Ace, providing a user-friendly graphical user interface, and allowing batch processing of several EPUB files. Available in German and English.
  • Ace plugin for Sigil. It allows to run Ace checks directly from the Sigil EPUB editor. Check this screencast for a quick demo.
  • Ace plugin for Calibre, developed by @thiagoeec. It allows to run Ace checks directly from Calibre, the ebook manager.

Language localizations

Please visit the localization wiki page to learn about translations.

Developer Workflow

Please visit the developer workflow wiki page for detailed developer-oriented information.