Daisy Consortium announces beta release of EPUB 3 accessibility checker

15 October 2017 | Ted Page

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Ace (Accessibility Checker for EPUB)

The Daisy Consortium has this week announced the first public beta release of Ace (Accessibility Checker for EPUB)—an open source command line accessibility conformance checker for EPUB 3. This is another welcome step forward in the world of EPUB accessibility, which is moving on apace. 


Ace will run a range of automated checks against the EPUB Accessibility Conformance and Discovery Specification 1.0. It will also check rules defined in WCAG and ARIA referenced by the EPUB specification.

Amongst Ace’s specific listed features are the ability to extract the navigational tables of contents, and images and their associated descriptions (i.e. the contents of the alt, figcaption or aria-describedby attributes) for ease of inspection. Intriguingly, it also checks metadata, including accessibility metadata. 

The limitations of automated testing

The InclusivePublishing.org Getting Started guide rightly points out that automated testing is only a part of the accessibility checking process, and should only be seen as an aid to evaluation by humans, and not a substitute for it. We have long since been making the same point with respect to over-reliance on automated PDF accessibility checkers which can be very useful tools, as long as their limitations are properly understood.

Development timescale

Ace is aimed at technical experts in the publishing industry, familiar with EPUB 3 code and comfortable with command line technologies.  We will certainly be looking to road-test it over the coming days and weeks, and to make any contribution we can. Final release is scheduled for around the end of the year.