Accessible Web

The web is inherently accessible

"Your weekly reminder that the web is accessible by default and it's our design decisions that stop it being accessible #a11y" — Kevin Mar-Molinero on Twitter, 7 December 2020

Why did you have to disable CSS to view this website? No reason other than a design choice that excludes sighted people.

Did you know? This is how many visitors "view" webpages already:

This website is fully accessible to people with screen readers and Braille displays. But many websites are not due to poor design choices that exclude some people.

What is web accessibility?

When a page is accessible, it was developed with the intention of working for as many people with disabilities as possible. A good place to start learning is the W3C's Introduction to Web Accessibility. Find out the different ways people with disabilities interact with the web.

Web Content Accessibility Guidelines (WCAG)

WCAG is a set of success criteria for determining if a page is accessible, led by four guiding principles:

Perceivable
Information and user interface components must be presentable to users in ways they can perceive.
Operable
User interface components and navigation must be operable.
Understandable
Information and the operation of the user interface must be understandable.
Robust
Content must be robust enough that it can be interpreted by a wide variety of user agents, including assistive technologies.

These contain guidelines and a hierarchy of success criteria from Level A to Level AAA. Many accessibility laws, and current best practice, point to WCAG 2.1 Level AA compliance. There are 50 discrete success criteria to evaluate, though many are not applicable to all pages. For example, if a page doesn't contain video, you don't have to evaluate against success criteria for captions or audio descriptions.

See the full list of success criteria

Did you know? The WCAG guidelines were first published in 1999. Web accessibility is not a new concept but a lot of people are learning about it only now.

Semantics

So what's the point? The point is to develop accessible pages from the bottom up, starting with semantic HTML. A whole lot of developers think they know HTML but are actually pretty sloppy about it. Many don't think it matters if they use a link or a button, but it does. Every semantic mistake introduces accessibility issues into your code. If you've never really "learned" HTML, check out this beginner's guide to writing good HTML.

By far, CSS color contrast issues are the most frequent accessibility issues I see, but the HTML ones are problematic too. Outlined below are the top HTML-related accessibility issues I encounter.

Headings

If you visually scan this page, you can quickly see how it is broken up into sections. That's due to using headings or the h1-h6 elements. It's important that every page have at least one h1 so people and search engines know what the topic of the page is. From there, cascade down to h2, h3, and so on.

Did you know? People using screen readers can navigate by headings in much the same way that sighted people can visually scan the page for items of importance.

Buttons and links may seem similar but they have very different semantic uses. If you use them interchangeably, people can get confused about what a button or link is going to do when activated.

Buttons

Buttons are used for controlling actions on the page, such as a form submit button or toggle button.

It's preferable to use a native button element instead of creating a custom one:

The button element can have various states depending on its purpose:

Collapsed
Expanded
Not pressed
Pressed

Links

Links are used for navigation, literally for linking to another page or place on the same page. When you use a link, people expect to go somewhere new when it's activated.

It's important that the link text properly convey the link purpose. Avoid generic text like "click here".

Same page link
Headings
New page link
Accessible Web tool
External link
Electronic Frontier Foundation
Email link
info@eff.org

Images

The one thing about accessibility most people know is that many images need a text equivalent. This may seem straightforward but let's look at three examples.

  1. Alt text

    Semantically speaking, every image needs an alt="" attribute. This alone will pass an automated accessibility checker. If an image is purely decorative, you can even leave the alt value empty.

    But if an image provides context to the content, the alt text must acurately describe the content of the image for people who cannot see it. The alt text for the image below is two cats on an easy chair under a blanket.

    two cats on an easy chair under a blanket

  2. SVG icons

    Inline SVG doesn't support the alt attribute. For meaningfult icons, add role="img" to the svg element to identify it as an image. Give it an accessible name using the aria-label attribute on the svg element.

    For decorative icons, hide the icon from assistive technology by adding the aria-hidden attribute to the svg element.

  3. SVG charts and graphs

    The value of the aria-label attribute for the following graph is bar chart showing the years 2016 to 2021 as the percentage of US consumers with a streaming video service increased from 52% to 78%.

    Go to the Tables section for information on providing access to all data points in the graph.

    US Consumers 52% 64% 69% 74% 78% 78% 2016 2017 2018 2019 2020 2021 0 20% 40% 60% 80% 100%

Tables

There are many legitimate uses for tables on the web but they are often coded incorrectly. Table data cells need corresponding table headers. This allows the applicable table header to be read by a screen reader before the table data cell contents. Additionally, tables need captions to provide a description of the table to people using screen readers.

In the SVG charts and graphs example under Images, we looked at a svg bar chart where we provided a snapshot of the data using aria-label. We need to provide all the data in a format that assistive technology can navigate and an easy way to do that is to provide all data points in a table.

US consumers with a streaming video subscription
Year US Consumers
2016 52%
2017 64%
2018 69%
2019 74%
2020 78%
2021 78%

Forms

Every input needs a label. It's really that simple. The label needs to be visible and persistent (avoid using placeholder). This helps people remember what information they've entered. Programatically link each pair using the for attribute on the label matching the id attribute on the input.

This enables a couple things:

Many modern browsers do cursory form field validation with the required attribute though error messages are not always accessible. Let assistive technology users know when a field is required by adding the aria-required="true" attribute to inputs.

When you have a group of related form fields, like checkboxes or radio buttons, group them with a fieldset element and provide an accessible name for the group with a legend element.

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In summary