Moodle accessibility

Moodle Accessibility (WCAG 2.1 AA)

Overview

Moodle targets WCAG 2.1 AA. UI in plugins must follow same standard for inclusion. Boost theme + Bootstrap 5 + Moodle's component library do most of the heavy lifting — your job is to use them correctly.

When to Use

• Building any UI (Mustache template, modal, custom form element)
• Reviewing PR for accessibility regression
• Submission to moodle.org plugin directory (a11y is reviewed)
• Responding to a user-reported a11y bug

Top rules

1. Use semantic HTML: <button> for actions, <a> for navigation, <h1>–<h6> in order
2. Every interactive element keyboard-reachable with visible :focus
3. Every image has alt; decorative images: alt=""
4. Color contrast ≥ 4.5:1 (text), 3:1 (UI components)
5. Forms: <label for> linked to every input
6. Don't use color alone to convey meaning
7. Modals trap focus, restore on close

Semantic Mustache

{{! BAD }}
<div class="btn" onclick="...">Save</div>

{{! GOOD }}
<button type="submit" class="btn btn-primary">{{#str}}save, core{{/str}}</button>

Headings:

<h2 id="ann-heading">{{#str}}announcements, local_example{{/str}}</h2>
<section aria-labelledby="ann-heading">...</section>

Skip levels = WCAG fail. <h2> then <h4> is wrong.

Forms — formslib

MoodleQuickForm outputs <label for> automatically. Don't bypass:

$mform->addElement('text', 'name', get_string('name', 'local_example'));
$mform->setType('name', PARAM_TEXT);
$mform->addRule('name', null, 'required', null, 'client');

// Help button — adds aria-described relationship
$mform->addHelpButton('name', 'name', 'local_example');

For required fields, addRule('required') adds aria-required="true".

Buttons / links

Element	Use for
<button type="submit">	Form submit
<button type="button">	JS action
<a href="...">	Navigation to a URL

Never <a href="#" onclick> — use <button>. Never <div role="button"> unless you also handle keyboard (Enter + Space) and focus.

Icons

{{#pix}}t/edit, core, {{#str}}edit, core{{/str}}{{/pix}}

Pix renderer outputs <img alt="..."> with the title as alt. For decorative icons accompanying visible text:

<button>
  {{#pix}}t/edit, core{{/pix}}<span class="visually-hidden"></span>
  {{#str}}edit, core{{/str}}
</button>

Bootstrap 5: .visually-hidden (was .sr-only in BS4).

Color contrast

Boost defines $primary, $secondary, etc. Don't override to low-contrast values.

// theme/yourtheme/scss/post.scss
$primary: #0f6fc5;     // contrast vs white = 5.13:1 ✓
$danger:  #d9534f;     // contrast vs white = 3.34:1 ✗ — fails AA for text

Test: https://webaim.org/resources/contrastchecker/

Don't rely on color only:

{{! BAD — color only }}
<span class="text-danger">{{name}}</span>

{{! GOOD — icon + color }}
<span class="text-danger">
  {{#pix}}t/error, core, {{#str}}invalid, local_example{{/str}}{{/pix}}
  {{name}}
</span>

Tables

<table class="table">
  <caption>{{#str}}attendance, local_example{{/str}}</caption>
  <thead>
    <tr>
      <th scope="col">{{#str}}user, core{{/str}}</th>
      <th scope="col">{{#str}}status, core{{/str}}</th>
    </tr>
  </thead>
  <tbody>
    {{#rows}}
    <tr>
      <th scope="row">{{name}}</th>
      <td>{{status}}</td>
    </tr>
    {{/rows}}
  </tbody>
</table>

html_table from lib/outputcomponents.php renders accessibly:

$table = new \html_table();
$table->head = [get_string('name'), get_string('status')];
$table->headspan = [1, 1];
$table->caption = get_string('attendance', 'local_example');
echo \html_writer::table($table);

ARIA — minimal use

Native HTML > ARIA. Only add ARIA when no native equivalent.

{{! tab pattern — needs ARIA }}
<div role="tablist" aria-label="{{#str}}sections, local_example{{/str}}">
  <button role="tab" aria-selected="true" aria-controls="panel-1" id="tab-1">One</button>
  <button role="tab" aria-selected="false" aria-controls="panel-2" id="tab-2">Two</button>
</div>
<div role="tabpanel" id="panel-1" aria-labelledby="tab-1">...</div>

Bootstrap 5 tab JS handles arrow keys. Don't reimplement.

Modals

Use core/modal — handles focus trap, ESC key, focus restore on close.

import Modal from 'core/modal';

const modal = await Modal.create({
    title: await getString('confirm', 'core'),
    body: await Templates.render('local_example/confirm', {}),
    show: true,
    removeOnClose: true,
});
// focus auto-traps inside; on close, focus returns to trigger element

Custom focus management:

import {trapFocus} from 'core/local/aria/focusmanager';
const release = trapFocus(modalEl);
// ... when closing:
release();
triggerEl.focus();

Live regions (toasts, async updates)

import {add as addToast} from 'core/toast';
addToast('Saved', {type: 'success'});

core/toast uses aria-live="polite". For urgent alerts: aria-live="assertive" (sparingly — interrupts screen readers).

Keyboard

Every interactive control:

• Focusable in source order (don't tabindex="0" everything)
• Activated with Enter / Space
• Visible focus ring (don't outline: 0 without replacement)
• Custom widgets follow WAI-ARIA Authoring Practices

Screen reader testing

OS	SR	Browser
Windows	NVDA (free)	Firefox
macOS	VoiceOver	Safari
Linux	Orca	Firefox
iOS	VoiceOver	Safari
Android	TalkBack	Chrome

Quick checks:

• Tab through entire UI — every interactive element reachable
• Use SR-only — does the experience make sense?
• Resize text 200% — layout still works?
• Disable CSS — content order still meaningful?

Automation

# axe-core via Puppeteer
npm install -g @axe-core/cli
axe http://localhost:8000/local/example/

# Pa11y
npm install -g pa11y
pa11y --standard WCAG2AA http://localhost:8000/local/example/

CI integration: run on PRs against staging.

Common Mistakes

Mistake	Fix
<div onclick>	<button>
Missing alt on <img>	Add — alt="" if decorative
placeholder as label	Add real <label for>
outline: 0 no replacement	Restore visible focus indicator
Heading level skip	Sequential <h1>/<h2>/<h3>
Link text "click here" / "more"	Descriptive (Edit user "Alice")
role="button" without keyboard	Use <button> instead
Color-only error indication	Add icon + text
Color contrast < 4.5:1	Adjust SCSS palette
Modal without focus trap	Use core/modal
aria-label on a <div> with no role	Either add role or use text instead
aria-hidden="true" on focusable element	Either unhide or remove from tab order

Plugin directory review

moodle.org reviewers run a11y checks. Common rejection reasons:

• New custom modal without focus trap
• Hard-coded colors failing AA contrast
• Custom widgets without ARIA / keyboard
• Missing <label> on form fields

References

• Accessibility: https://moodledev.io/general/development/policies/accessibility
• WCAG 2.1: https://www.w3.org/TR/WCAG21/
• WAI-ARIA APG: https://www.w3.org/WAI/ARIA/apg/
• Boost a11y: https://docs.moodle.org/dev/Boost_-_Accessibility
• pix renderer: https://moodledev.io/docs/apis/subsystems/output#pix-icons