WCAG 3.2.3 Consistent Navigation in reflowable EPUB?

[gregoriopellegrino]

Section

No response

Describe the problem

I think interpreting the success criterion for WCAG 3.2.3 (Consistent Navigation) in the context of reflowable EPUBs is complex. Can we discuss this in relation to EPUB Accessibility 1.2?

Describe the fix or new feature you propose

No response

[mattgarrish]

(Switching the label to the accessibility techniques as that's where we discuss how to apply wcag SC.)

How do you find this applies to reflowable epubs? I've struggled to come up with real use cases for it over the years as reflowable epubs reflowable don't often repeat the same kinds of content, and it's a bit of a stretch to say that users depend on visual or spatial layout for locating such repeated content.

The web case makes more sense since each page is framed by the repeated nevigation content that this is targeting (the stuff that is outside of the main content area like skip to content links, menu bars, breadcrumbs, etc.).

The only case I've ever come across is if you have something like an "in this chapter" set of quick links that get repeated, which by the SC you could claim always need to be placed in the same spot (e.g., after the chapter heading).

But I'd be happy to have this formally documented rather than have to claim it myself in the kb, etc.

[sueneu]

Hello @gregoriopellegrino

I think interpreting the success criterion for WCAG 3.2.3 (Consistent Navigation) in the context of reflowable EPUBs is complex.

This specification seems more applicable to reading systems, who set the navigational environment. Like asking that the link to the TOC is in a predictable place across the reading platform and doesn't change while reading a book in a specific viewport size/orientation. I could see that consistency of rs navigation would be complex across viewport sizes and orientations and reader preferences.

Are you thinking of navigation created within the ebook by an author like @mattgarrish said?

The only case I've ever come across is if you have something like an "in this chapter" set of quick links that get repeated, which by the SC you could claim always need to be placed in the same spot (e.g., after the chapter heading).

[mattgarrish]

This specification seems more applicable to reading systems, who set the navigational environment.

And then it would fall under the purview of UAAG not WCAG - although UAAG doesn't have a requirement like this for user agents.

The applications for EPUB authoring are few and far between. You could make a case for fixed layouts that if page numbering is specified in each document it needs to be consistently located. That would match up with the PDF technique for the success criterion, but the same can't apply to reflowable numbers.

The other PDF technique specifies that you should set running headers and footers, which even for FXL EPUBs is another case where the reading system usually controls the behaviour, not the author.

[murata2makoto]

I think this question is not limited to WCAG 3.2.3 alone. There seems to be a broader pattern here.

Several related success criteria appear to rely on the same underlying assumption of repeated navigation structures across pages, which does not generally hold for reflowable EPUBs:

• 2.4.1 Bypass Blocks — assumes the presence of repeated blocks of content (e.g., navigation menus) that users need to skip.
• 2.4.5 Multiple Ways — assumes a site-like structure where multiple navigation mechanisms (search, menus, etc.) are provided by the content.
• 3.2.4 Consistent Identification — assumes consistent UI components whose labeling or identification is controlled by the content.

In reflowable EPUBs:

• Repeated navigation structures are typically absent or minimal.
• Navigation is largely provided by the navigation document and reading system, not the other content documents.
• UI components are not under the control of the author.

As a result, these success criteria—like 3.2.3—may have limited or unclear applicability to EPUB content, except in specific cases (e.g., intentionally repeated intra-publication navigation like “in this chapter” links).

It might be useful to consider whether this is a broader applicability issue for WCAG navigation-related success criteria in EPUB, rather than treating 3.2.3 in isolation.

[mattgarrish]

• 2.4.5 Multiple Ways — assumes a site-like structure where multiple navigation mechanisms

We already address multiple ways in the techniques - it always passes because the table of contents and spine provide two methods of navigating the content.

• 2.4.1 Bypass Blocks

Yes, this is another one that's not relevant to epubs. Even if you were to consider running headers in a FXL document a repeated block, nobody wants a "skip to content" link at the start of each page.

• 3.2.4 Consistent Identification

Not sure I agree with you entirely on this one. There are some aspects in the WCAG explanation that likely would never apply, but I don't think it's possible to say the success criterion itself never applies. A simple example off the top of my head would be if you use an icon to identify a link to an extended description, or one to identify external hyperlinks. The text alternatives in these cases need to be consistent throughout the book.

[mattgarrish]

• 2.4.1 Bypass Blocks

Yes, this is another one that's not relevant to epubs.

Should have double-checked. This is also already covered in the techniques, too.

[sueneu]

3.2.4 Consistent Identification — assumes consistent UI components whose labeling or identification is controlled by the content.

I wondered if this might apply to complex reflowable titles that feature additional content like a sidebar or extended bio in each chapter. Then this might require the markup to be consistent for each type of content in all the places it appears.

[mattgarrish]

Then this might require the markup to be consistent for each type of content in all the places it appears.

This always comes to mind for me, too, but it's not really in scope. The example I always think of is if you use an image of a lit bomb to identify a sidebar that identifies a danger, the alt text or label for the aside should be consistent.

But a sidebar isn't an interactive component and the definition for the success criterion is:

Components that have the same functionality within a set of web pages are identified consistently.

Its focus is only on ensuring consistency in aspects of the content that users interact with.