Accessible Styles

We've explored two of the crucial pillars of accessibility, focus and semantics. Now let's tackle the third, styling. It's a broad topic that we can cover in three sections.

  • Ensuring that elements are styled to support our accessibility efforts by adding styles for focus and various ARIA states.
  • Styling our UIs for flexibility so they can be zoomed or scaled to accommodate users who may have trouble with small text.
  • Choosing the right colors and contrast to avoid conveying information with color alone.

Styling focus

Generally, any time we focus an element, we rely on the built-in browser focus ring (the CSS outline property) to style the element. The focus ring is handy because, without it, it's impossible for a keyboard user to tell which element has the focus. The WebAIM checklist makes a point of this, requiring that "It is visually apparent which page element has the current keyboard focus (i.e., as you tab through the page, you can see where you are)."

form elements with a focus ring

However, sometimes the focus ring can look distorted or it may just not fit in with your page design. Some developers remove this style altogether by setting the element's outline to 0 or none. But without a focus indicator, how is a keyboard user supposed to know which item they're interacting with?

You might be familiar with adding hover states to your controls using the CSS :hover pseudo-class. For example, you might use :hover on a link element to change its color or background when the mouse is over it. Similar to :hover, you can use the :focus pseudo-class to target an element when it has focus.

/* At a minimum you can add a focus style that matches your hover style */
:hover, :focus {
  background: #c0ffee;

An alternative solution to the problem of removing the focus ring is to give your element the same hover and focus styles, which solves the "where's-the-focus?" problem for keyboard users. As usual, improving the accessibility experience improves everyone's experience.

Input modality

a native HTML button with a focus ring

For native elements like button, browsers can detect whether user interaction occurred via the mouse or the keyboard press, and typically only display the focus ring for keyboard interaction. For example, when you click a native button with the mouse there is no focus ring, but when you tab to it with the keyboard the focus ring appears.

The logic here is that mouse users are less likely to need the focus ring because they know what element they clicked. Unfortunately there isn't currently a single cross-browser solution that yields this same behavior. As a result, if you give any element a :focus style, that style will display when either the user clicks on the element or focuses it with the keyboard. Try clicking on this fake button and notice the :focus style is always applied.

  fake-button {
    display: inline-block;
    padding: 10px;
    border: 1px solid black;
    cursor: pointer;
    user-select: none;

  fake-button:focus {
    outline: none;
    background: pink;
<fake-button tabindex="0">Click Me!</fake-button>

This can be a bit annoying, and often times developer will resort to using JavaScript with custom controls to help differentiate between mouse and keyboard focus.

In Firefox, the :-moz-focusring CSS pseudo-class allows you to write a focus style that is only applied if the element is focused via the keyboard, quite a handy feature. While this pseudo-class is currently only supported in Firefox, there is currently work going on to turn it into a standard.

There is also this great article by Alice Boxhall and Brian Kardell that explores the topic of modality and contains prototype code for differentiating between mouse and keyboard input. You can use their solution today, and then include the focus ring pseudo-class later when it has more widespread support.

Styling states with ARIA

When you build components, it's common practice to reflect their state, and thus their appearance, using CSS classes controlled with JavaScript.

For example, consider a toggle button that goes into a "pressed" visual state when clicked and retains that state until it is clicked again. To style the state, your JavaScript might add a pressed class to the button. And, because you want good semantics on all your controls, you would also set the aria-pressed state for the button to true.

A useful technique to employ here is to remove the class altogether, and just use the ARIA attributes to style the element. Now you can update the CSS selector for the pressed state of the button from this

.toggle.pressed { ... }

to this.

.toggle[aria-pressed="true"] { ... }

This creates both a logical and a semantic relationship between the ARIA state and the element's appearance, and cuts down on extra code as well.

Multi-device responsive design

We know that it's a good idea to design responsively to provide the best multi-device experience, but responsive design also yields a win for accessibility.

Consider a site like at 100% magnification

A low-vision user who has difficulty reading small print might zoom in the page, perhaps as much as 400%. Because the site is designed responsively, the UI will rearrange itself for the "smaller viewport" (actually for the larger page), which is great for desktop users who require screen magnification and for mobile screen reader users as well. It's a win-win. Here's the same page magnified to 400%: at 400% magnification

In fact, just by designing responsively, we're meeting rule 1.4.4 of the WebAIM checklist, which states that a page "...should be readable and functional when the text size is doubled."

Going over all of responsive design is outside the scope of this guide, but here are a few important takeaways that will benefit your responsive experience and give your users better access to your content.

  • First, make sure you always use the proper viewport meta tag.
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    Setting width=device-width will match the screen's width in device-independent pixels, and setting initial-scale=1 establishes a 1:1 relationship between CSS pixels and device-independent pixels. Doing this instructs the browser to fit your content to the screen size, so users don't just see a bunch of scrunched-up text.

a phone display without and with the viewport meta tag

  • Another technique to keep in mind is designing with a responsive grid. As you saw with the Udacity site, designing with a grid means your content will reflow when the page changes size. Often these layouts are produced using relative units like percents, ems, or rems instead of hard-coded pixel values. The advantage of doing it this way is that text and content can enlarge and force other items down the page. So the DOM order and the reading order remain the same, even if the layout changes because of magnification.

  • Also, consider using relative units like em or rem for things like text size, instead of pixel values. Some browsers support resizing text only in user preferences, and if you're using a pixel value for text, this setting will not affect your copy. If, however, you've used relative units throughout, then the site copy will update to reflect the user's preference.

  • Finally, when your design is displayed on a mobile device, you should ensure that interactive elements like buttons or links are large enough, and have enough space around them, to make them easy to press without accidentally overlapping onto other elements. This benefits all users, but is especially helpful for anyone with a motor impairment.

A minimum recommended touch target size is around 48 device independent pixels on a site with a properly set mobile viewport. For example, while an icon may only have a width and height of 24px, you can use additional padding to bring the tap target size up to 48px. The 48x48 pixel area corresponds to around 9mm, which is about the size of a person's finger pad area.

a diagram showing a couple of 48 pixel touch targets

Touch targets should also be spaced about 32 pixels apart, both horizontally and vertically, so that a user's finger pressing on one tap target does not inadvertently touch another tap target.

a diagram showing 32 pixels of space around a touch target

Color and contrast

If you have good vision, it's easy to assume that everyone perceives colors, or text legibility, the same way you do — but of course that's not the case. Let's wrap things up by looking at how we can effectively use color and contrast to create pleasant designs that are accessible to everyone.

As you might imagine, some color combinations that are easy for some people to read are difficult or impossible for others. This usually comes down to color contrast, the relationship between the foreground and background colors' luminance. When the colors are similar, the contrast ratio is low; when they are different, the contrast ratio is high.

The WebAIM guidelines recommend an AA (minimum) contrast ratio of 4.5:1 for all text. An exception is made for very large text (120-150% larger than the default body text), for which the ratio can go down to 3:1. Notice the difference in the contrast ratios shown below.

comparison of various contrast ratios

The contrast ratio of 4.5:1 was chosen for level AA because it compensates for the loss in contrast sensitivity usually experienced by users with vision loss equivalent to approximately 20/40 vision. 20/40 is commonly reported as typical visual acuity of people at about age 80. For users with low vision impairments or color deficiencies, we can increase the contrast up to 7:1 for body text.

You can use the Accessibility DevTools extension for Chrome to identify contrast ratios. One benefit of using the Chrome Devtools is that they will suggest AA and AAA (enhanced) alternatives to your current colors, and you can click the values to preview them in your app.

To run a color/contrast audit, follow these basic steps.

  1. After installing the extension, click Audits
  2. Uncheck everything except Accessibility
  3. Click Audit Present State
  4. Note any contrast warnings

the devtools contrast audit dialog

WebAIM itself provides a handy color contrast checker you can use to examine the contrast of any color pair.

Don't convey information with color alone

There are roughly 320 million users with color vision deficiency. About 1 in 12 men and 1 in 200 women have some form of "color blindness"; that means about 1/20th, or 5%, of your users will not experience your site the way you intended. When we rely on color to convey information, we push that number to unacceptable levels.

For example, in an input form, a telephone number might be underlined in red to show that it is invalid. But to a color deficient or screen reader user, that information is not conveyed well, if at all. Thus, you should always try to provide multiple avenues for the user to access critical information.

an input form with an error underlined in red

The WebAIM checklist states in section 1.4.1 that "color should not be used as the sole method of conveying content or distinguishing visual elements." It also notes that "color alone should not be used to distinguish links from surrounding text" unless they meet certain contrast requirements. Instead, the checklist recommends adding an additional indicator such as an underscore (using the CSS text-decoration property) to indicate when the link is active.

An easy way to fix the previous example is to add an additional message to the field, announcing that it is invalid and why.

an input form with an added error message for clarity

When you're building an app, keep these sorts of things in mind and watch out for areas where you may be relying too heavily on color to convey important information.

If you're curious about how your site looks to different people, or if you rely heavily on the use of color in your UI, you can use the NoCoffee Chrome extension to simulate various forms of visual impairment, including different types of color blindness.

High contrast mode

High-contrast mode allows a user to invert foreground and background colors, which often helps text stand out better. For someone with a low vision impairment, high-contrast mode can make it much easier to navigate the content on the page. There are a few ways to get a high-contrast setup on your machine.

Operating systems like Mac OSX and Windows offer high-contrast modes that can be enabled for everything at the system level. Or users can install an extension, like the Chrome High Contrast extension to enable high-contrast only in that specific app.

A useful exercise is to turn on high-contrast settings and verify that all of the UI in your application is still visible and usable.

For example, a navigation bar might use a subtle background color to indicate which page is currently selected. If you view it in a high-contrast extension, that subtlety completely disappears, and with it goes the reader's understanding of which page is active.

a navigation bar in high contrast mode

Similarly, if you consider the example from the previous lesson, the red underline on the invalid phone number field might be displayed in a hard-to-distinguish blue-green color.

a form with an error field in high contrast mode

If you are meeting the contrast ratios covered in the previous lessons you should be fine when it comes to supporting high-contrast mode. But for added peace of mind, consider installing the Chrome High Contrast extension and giving your page a once-over just to check that everything works, and looks, as expected.