Hiding Content Responsibly

By Kitty Giraudel

I wrote about hiding content during the A11yAdvent calendar, namely how to make something invisible but still accessible for screen readers. I’m going to mention the “accessibility tree” a few times in this article, so be sure to read how accessibility trees inform assistive technologies by Hidde de Vries.

In this article, I want to discuss all the ways to hide something, be it through HTML or CSS, and when to use which. Feel free to jump to the summary.

Overview

Method Visible Accessible
.sr-only class No Yes
aria-hidden="true" Yes No
hidden="" No No
display: none No No
visibility: hidden No, but space remains No
opacity: 0 No, but space remains Depends
clip-path: circle(0) No, but space remains Depends
transform: scale(0) No, but space remains Yes
width: 0 + height: 0 No No
content-visibility: hidden No No

The .sr-only class

This combination of CSS declarations hides an element from the page, but keeps it accessible for screen readers. It comes in very handy to provide more context to screen readers when the visual layout is enough with it.

Summary:

  • Visible: no (removed from layout)
  • Accessible: yes
  • Element + children focusable: yes (⚠️)

Verdict: 👍 Great to visually hide something while preserving it for assistive technologies.

The aria-hidden HTML attribute, when set to true, hides the content from the accessibility tree, while keeping it visually visible. That is because no browser applies any styling to elements aria-hidden="true" (which is a good thing).

Summary:

  • Visible: yes
  • Accessible: no (except via aria-describedby and aria-labelledby)
  • Element + children focusable: yes (⚠️)

Verdict: 👍 Great to hide something from assistive technologies while keeping it visually displayed. Use with caution.

The display: none declaration and the hidden attribute

The display: none declaration and the hidden HTML attribute do the same thing: they visually remove an element from the rendering tree and from the accessibility tree.

What’s nice about the hidden attribute is that you can mask content entirely through HTML without having to write any CSS, which can be handy in some context.

Summary:

  • Visible: no (removed from layout)
  • Accessible: no (except via aria-describedby and aria-labelledby)
  • Element + children focusable: no

Verdict: 👍 Great to hide something from both assistive technologies and screens.

The visibility: hidden CSS declaration visually hides an element without affecting the layout. The space it takes remains empty and surrounding content doesn’t reflow in its place.

From the accessibility perspective, the declaration behave like display: none and the content is removed entirely and not accessible.

Summary:

  • Visible: no (remains in layout)
  • Accessible: no
  • Element + children focusable: no

Verdict: 👍 Good when display: none is not an option and the layout permits it.

The opacity: 0, clip-path: circle(0) declarations

The opacity: 0 and clip-path: circle(0) CSS declarations visually hide an element, but the place it takes is not freed, just like visibility: hidden.

Whether the content remains accessible depends on assistive technologies. Some will consider the content inaccessible and skip it, and some will still read it. For that reason, it is recommended not to use these declarations to consistently hide content.

Summary:

  • Visible: no (remains in layout)
  • Accessible: depends
  • Element + children focusable: yes (⚠️)

Verdict: Shady and inconsistent, don’t expect for visual animations purposes.

The transform: scale(0) declaration

The transform: scale(0) CSS declaration visually hides an element, but the place it takes is not freed, just like visibility: hidden, opacity: 0 and clip-path: circle(0).

The content remains accessible to screen readers though.

Summary:

  • Visible: no (remains in layout)
  • Accessible: yes
  • Element + children focusable: yes

Verdict: Restrict for visual animations purposes.

The width: 0 and height: 0 declarations

Resizing an element to a 0x0 box with the width and height CSS properties and hiding its overflow will cause the element not to appear on screen and as far as I know all screen readers will skip it as inaccessible. However, this technique are usually considered quite fishy and could cause SEO penalties.

Summary:

  • Visible: no (removed from layout)
  • Accessible: no
  • Element + children focusable: no

Verdict: 👎 Unclear and unexpected, risky from a SEO perspective, don’t.

The content-visibility: hidden declaration

The content-visibility CSS property was introduced as a way to improve performance by hinting the browser (Chrome, as of writing) to skip rendering of a certain element until it is within the viewport.

Content made hidden with content-visibility: hidden will effectively be absent from the accessibility tree entirely (just like with display: none). This is not necessarily intended behaviour though, and for that reason it is recommended not to use that declaration on landmarks.

Summary:

  • Visible: no (removed from layout)
  • Accessible: no
  • Element + children focusable: no

Verdict: 👎 Poor support, poorly implemented, don’t.

Generally speaking, you want to avoid having too many discrepancies between the visual content, and the underlying content exposed to the accessibility layer. The more in sync they are, the better for everyone. Remember that a clearer visual interface with more explicit content benefits everyone.

  • If you need to hide something both visually and from the accessibility tree, use display: none or the hidden HTML attribute. Valid cases: show/hide widget, offscreen navigation, closed dialog.

  • If you need to hide something from the accessibility tree but keep it visible, use aria-hidden="true". Valid cases: visual content void of meaning, icons.

  • If you need to visually hide something but keep it accessible, use the visually hidden CSS declaration group. Valid cases: complementary content to provide more context, such as for icon buttons/links.