Underlined links for accessibility

[Rob Beezer]

There is a request on the -a11y group for undelined links in PDF out for
accessibility reasons.

https://groups.google.com/g/pretext-a11y/c/e1t-JQScUsA/m/CWflKbwuDwAJ

Before we make a publisher switch, do we want this to be LaTeX-only, or "common"
(i.e. HTML).

What do the style and CSS folks think. I could see this being a bad style
choice. But maybe good for accessibility (I hope to hear more on -a11y).

Reasonably easy to accomodate in CSS once a switch is built? We'd need a
volunteer for that.

Rob

[Andrew Scholer]

Yes, that would be a good switch to have. I think there is a good accessibility based case that underlines on should be the default in HTML. Though adding them to the current bold might be too dark visually and make reading inline links that are part of a sentence harder.

The biggest gotcha will be making sure they are only applied to links in the body and not things like the ToC, summary page links, etc.... I also could see them being undesired in things like interactives. So we might need to add extra classes to body based links generated by PTX.

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[Rob Beezer]

On 3/26/26 11:24, Andrew Scholer wrote:
> Yes, that would be a good switch to have. I think there is a good accessibility
> based case that underlines on should be the default in HTML. Though adding them
> to the current bold might be too dark visually and make reading inline links
> that are part of a sentence harder.

My thought for LaTeX is that it would be opt-in. But as we rely on HTML for the
best accessible experience, perhaps it should be opt-out? So maybe we need two
switches? Not a problem, in my view.

> The biggest gotcha will be making sure they are only applied to links in the
> body and not things like the ToC, summary page links, etc.... I also could see
> them being undesired in things like interactives. So we might need to add extra
> classes to body based links generated by PTX.

Right now, I'm thinking #xref and #url. So we could add classes as part of
manufacturing those. Maybe there are some one-off we do want? (Not thinking of
any right this minute.)

Rob

> On Thu, Mar 26, 2026 at 10:59 AM 'Rob Beezer' via PreTeXt development <pretext-
> d...@googlegroups.com <mailto:prete...@googlegroups.com>> wrote:
>
> There is a request on the -a11y group for undelined links in PDF out for
> accessibility reasons.
>
> https://groups.google.com/g/pretext-a11y/c/e1t-JQScUsA/m/CWflKbwuDwAJ
> <https://groups.google.com/g/pretext-a11y/c/e1t-JQScUsA/m/CWflKbwuDwAJ>
>
> Before we make a publisher switch, do we want this to be LaTeX-only, or
> "common"
> (i.e. HTML).
>
> What do the style and CSS folks think.  I could see this being a bad style
> choice.  But maybe good for accessibility (I hope to hear more on -a11y).
>
> Reasonably easy to accomodate in CSS once a switch is built?  We'd need a
> volunteer for that.
>
> Rob
>
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>
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[Oscar Levin]

I definitely think a publisher switch for LaTeX is good.  For HTML, I think this is a theme decision.  If links are decorated differently (like in default modern being bold) then that is probably good enough.  

One thing I learned just this week: the color contrast between link text and surrounding text should be 3:1 if you don't underline links: https://webaim.org/blog/wcag-2-0-and-link-colors/.

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[Andrew Scholer]

If a theme decides to use underlines as the primary way to differentiate links, the publisher should not be able to turn that off.

If a theme uses bold or some other mechanism, it might be nice for the publisher to be able to "maximize" accessibility by forcing underlines. After playing for a few minutes in SA, I am not sure that should be on by default. Different kinds of links (knowl openers vs navigation) are currently indicated by different styling in default-modern (underline vs bold). To whatever degree that distinction ends up being figured out by readers, making everything underlined would make the difference less noticeable.

Clarifying Oscar's last item slightly... the 3:1 contrast is required only if the links aren't decorated differently (in any way), not when they are not underlined.

The 3:1 ratio comes from this technique:
https://www.w3.org/WAI/WCAG22/Techniques/general/G183

That is just one way to satisfy Success Criterion 1.4.1:
https://www.w3.org/WAI/WCAG22/quickref/?versions=2.0&showtechniques=141#use-of-color

Another way is:
https://www.w3.org/WAI/WCAG22/Techniques/general/G182

It specifies:
To use this technique, an author incorporates a visual cue in addition to color for each place where color alone is used to convey information. Visual cues can take many forms including changes to the font style, the addition of underlines, bold, or italics, or changes to the font size.

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[Rob Beezer]

I've implemented underlining for LaTeX, report on -a11y. Issue here:

https://github.com/PreTeXtBook/pretext/pull/2807

Thanks for the HTML discussion. So if this is a theme decision (which sounds
reasonable), do we have, or want, a theme that is maximally accessible?
Underlines, huge contrast, etc?

Which makes me think, this could even be a reader decision. Underlined links,
or no. A contrast slider. Configurable letter-spacing. That's right - David F
was once experimenting with exactly this - readability was the umbrella term, I
think. I think it would be great if somebody (David?) picked that up again.

Publishers don't want to post "special editions", I don't think. And each
reader's requirements and/or preferences could be very different.

Rob

[Oscar Levin]

Creeping up to the top of my todo list is creating an accessibility menu that gets added to all pretext books.  Or maybe those that don't opt out.  It will allow you to pick high contrast, large print, and more.  Even a screen reader.  Probably a summer project.

One thing I can't decide on is whether there should be a separate reader preference menu.  But that's a detail to decide later.

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[Rob Beezer]

On 3/27/26 16:51, Oscar Levin wrote:
> Creeping up to the top of my todo list

Excellent! When the time comes, let me know what I can do to help. -Rob