4.13 Validation + Accessibility Checker Tools

Making Ebooks with InDesign: Module 4, Step 13

  • Subject(s):

    InDesign to EPUB

  • Resource Type(s):


  • Audience:


Suggested Prerequisite

Before reading this, you might want to read:

Quality Assurance

The last thing I want to emphasize in this course of videos is that there are two free tools that you will want to use nearly constantly: EPUB Checker, and Ace by DAISY. They are indispensable to my workflows. 

EPUB Checker is exactly that — an EPUB validator. Some people find it a little frustrating to use because the error messages are a little tricky to wade through, especially for people new to making ebooks. You might find it useful to use EPUB Checker constantly as you are editing an ebook. The way I use it is this: I run an ebook and then fix one error at a time. And the reason I do this is twofold — partly to make sure that my fix takes care of the error message, and partly to make sure that I am not introducing a new error as I fix that one. If you’ve embedded fonts, you are almost certain to get some errors because of that. EPUB-Checker doesn’t like font encryption or TTF fonts. Both of those types of errors are safe to ignore. 

The report from EPUB Checker. It is pink and red because the EPUB has warnings and errors meaning it is not valid just yet.

In this screenshot, the errors that refer to fonts are all related to either the font format or the font encryption. Those can be ignored. 

Teasing through the other errors will take a bit of detective work. The first red error above refers to the content.opf and then gives the clue that the error is on line 72. An ebook exported from InDesign will have a number of IDs and sometimes, in the course of editing the garbage HTML, the IDs are deleted. That is very likely what those three red errors refer to. 

Ace, by DAISY is a new-ish tool. It is designed to give your ebooks a once over from an accessibility point of view. It will turn up errors which, again, might feel difficult to grok but you will get used to it. It will turn up errors related to a missing source ISBN, colour contrast issues, gaps in the cascade of headers, etc. It very helpfully categorized the errors into critical, serious, moderate, and minor. 

I love to use it to see a bird’s eye view of what’s happening in an ebook, particularly the headings outline. 

The outlines view from Ace by DAISY.

And under the images tab, you can clearly see the alt text, figcaptions, and roles applied to any images in one quick assemblage which is really useful — both for evaluating alt text (these descriptions are kind of dreadful, let’s admit it!), and for seeing any images that I missed. 

Next Steps


Final Quality Assurance (QA) Pass

Quality Assurance of Completed Ebooks

Once your ebook has been created, it is time to do a quality assurance check for accessibility. This resource contains both simplified and advanced checklists to help you review your ebooks.

Subject(s): Ebook Production
Resource Type(s): Checklist

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