transpect user group, 16.9.2022

What is ACE?

  • EPUB checking tool by DAISY consortium
  • reports accessibility issues
  • version 1.0 released on 29 January 2018

Before you start with ACE…

Check your EPUB with EPUBcheck first!
An invalid EPUB is by no means accessible.

Ace app

Ace for command line

Common issues

  • current version of accessibility guidelines not implemented yet
  • missing accessibility metadata
  • Untitled BODY
  • Element has no ARIA role matching its epub:type
  • alternative texts for equations and images

ACE in transpect

  • XProc wrapper for ACE on command line
  • converts JSON report to Schematron SVRL
  • included in HTML report

ACE in transpect

  • ACE check is only started when EPUB is valid
  • messages are included in EPUBcheck category
  • message severity can be overwritten (e.g. test mode)


  • report is a summary of all ACE messages
  • messages do not point to original error location
  • ACE seems pretty unstable for invalid EPUBs and “magically” crashes

Thank you
for your attention!