Accessibility Notes
My notes for making the web more inclusive. Don't follow this guide blindly. Read the references to learn more about certain rules.
Check out my general best practices for building better applications.
This page is a continuous work in progress.
Where to start?
Accessibility fundamentals are covered in the Web Fundamentals Guide (Google) and the Web Accessibility Course (Udacity/Google). Both resources are free.
To evaluate the accessibility of a web page, try out the following tools:
- Chrome/Firefox browser extension: WAVE
- Command line: evaluatory
Resources
- WCAG Quick Reference
- WAI-ARIA Authoring Practices 1.2
- A11y Reviews (GitHub)
- Accessibility interview questions
- IBM Accessibility Checklist 7.1
- Accessibility motivation
Collections
General
Best practices
- Provide a correct lang attribute.
- Ensure that interactive controls have at least a 44x44 pixels target click size.
Libraries
- Accessible, responsive canvas.
- a11y-dialog - Accessible JS modal dialog.
- Comica11y - accessible comics.
Tools / Audit
- Accessibility tools audit — An example page to test the effectiveness of accessibility tools.
- There are multiple issues with AccessiBe.
- Building the most inaccessible site possible with a perfect Lighthouse score.
Stories
- The WebAIM Million - An annual accessibility analysis of the top 1,000,000 home pages.
- Losing sight.
- I'm a software engineer going blind, how should I prepare?.
- A blog where the author describes their way to become certified in WAS and CPACC.
Focus indicator
- Don't disable outline, master it instead.
- It is not required that hover as a state is differentiated from the default (and presumably all other) states.
- Adjusting the flex order does not change the focus order.
- Provide a fallback for Windows High Contrast mode when using a
box-shadow
focus indicator. - A keyboard-only focus ring has pros and cons, but it is technically possible using
:focus-visible
. Progressive enhancement handles older browsers.
Colors / Contrast Ratio
Labels
- Alt-Texts — The Ultimate Guide.
- There are limitations of
aria-label
,aria-labelledby
andaria-describedby
. It's complicated. - Google Translate does not translate
aria-label
labels. - HTML for vs wrapping label.
Fonts
- There's no evidence that typefaces designed to help dyslexics have any effect.
- Accessible font types.
- Atkinson Hyperlegible Font.
WCAG / WAI-ARIA
- WCAG-compliant website showcase
- Rules for using ARIA.
- An in-depth guide to ARIA roles.
- A
password
role is under discussion.
Screen reader
- NVDA Keyboard Shortcuts
- User survey 2019 (browser/screen reader usage)
- Do not use screen reader detection.
Support
Announcement
- A screen reader may announce things differently than displayed in the text viewer. Pay attention to times, dates, currency, punctuation, special characters, emoji, math symbols, common (and uncommon) abbreviations & acronyms.
- Minus the minus - A PSA about screen readers and negative numbers.
- NVDA has fixed a related issue.
- Talkback doesn't recognize the
-
character correctly.
- Acronyms can usually be left as-is.
- NVDA announces values differently between divs and spans.
- Improve the announcement of phone numbers:
<a href="tel:703555121" aria-label="7 0 3. 5 5 5. 1 2 1.">(703) 555-121</a>
::before
and::after
content is screen reader accessible (except IE11).- CSS generated content is not fully accessible.
- A live region will announce changes coming from a CSS counter.
- Defining an alternative text for CSS
content
.
- How the
display
properties affect<table>
,<ul>
,<ol>
,<dl>
,<h#>
,<button>
. - German gender characters are not excluding screen reader users.
Elements and Widgets
Date Picker
Something I see (...) is the frustration with date fields that are anything other than a plain text field for well-known dates (like birthdays).
Definition Lists
<dl>
<dt>Coffee</dt>
<dd>Black hot drink</dd>
<dt>Milk</dt>
<dd>White cold drink</dd>
</dl>
- Wrappings divs are allowed.
- NVDA does not expose definition lists correctly, but:
It's worth noting that a definition list is the correct way to mark up a list of paired items. Changing markup patterns to satisfy the vagaries of specific assistive technologies tends to be a slippery slope. (source)
Dialog / Modal
- There is no fixed rule where the focus should be moved to after opening a modal. A headline of the dialog itself are two good possibilities.
Fieldset
- A
legend
has to be a direct child of afieldset
. A screen reader might not announce the label if the markup is malformed (e.g. NVDA). Solutions:- Use
role="group"
+aria-labelledby
instead. - Use a duplicate label
- Use
- There was a Chrome bug, making it impossible to adjust the
fieldset
display
value.
Footer
There are some rules regarding the <footer>
element:
- The HTML footer element defines a
contentinfo
landmark when its context is the body element. - The HTML footer element is not considered a contentinfo landmark when it is descendant of any of following elements:
article
,aside
,main
,nav
,section
A contentinfo landmark role is used to identify information repeated at the end of every page of a website, hence a page should not have more than one contentinfo landmark.
Headline
- Use a single H1 per page. It doesn't have to come first, though (example).
Images
- Decorational images:
We tried to outsmart screen readers by letting them skip descriptive images. This turned out to be really unhelpful. Users that are not fully blind will still see an image and when the screen reader skips these images, users will assume they missed out on information. Solution: let the screen reader tell the users it’s a descriptive image. Or even better, write a descriptive alt-text for images. source
- Background images are mostly ignored in Windows High Contrast mode.
Inputs
- Prefer
type="search"
for search inputs, even though it currently offers little benefit.
Links
- Accessible anchor links
- Mark links that open in a new window:
<div hidden>
<span id="new-window-0">Opens in a new window</span>
<span id="new-window-1">Opens an external site</span>
<span id="new-window-2">Opens an external site in a new window</span>
</div>
<a
href="https://example.com"
target="_blank"
rel="noopener"
aria-describedby="new-window-0"
>
My site
</a>
- Download links:
- Use
<a>
, not a<button>
. - Provide media type and file size visually readable.
- Use
- The trouble with mailto email links and what to do instead.
SVGs
<svg role="img">
<title>Lightbulb moment!</title>
<path d="..." />
</svg>
Tables
- Include a table caption:
<table>
<caption>
Populations of cities
</caption>
<thead>
...
</thead>
<tbody>
...
</tbody>
</table>
Tooltips
Video Player
- Why videos on GOV.UK use the YouTube video player.
- Don't rely on YouTube transcripts.