🤖system prompt•7 months ago
screen-reader-testing
Test web applications with screen readers including VoiceOver,
coding
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# Screen Reader Testing
Practical guide to testing web applications with screen readers for comprehensive accessibility validation.
## When to Use This Skill
- Validating screen reader compatibility
- Testing ARIA implementations
- Debugging assistive technology issues
- Verifying form accessibility
- Testing dynamic content announcements
- Ensuring navigation accessibility
## Core Concepts
### 1. Major Screen Readers
| Screen Reader | Platform | Browser | Usage |
| ------------- | --------- | -------------- | ----- |
| **VoiceOver** | macOS/iOS | Safari | ~15% |
| **NVDA** | Windows | Firefox/Chrome | ~31% |
| **JAWS** | Windows | Chrome/IE | ~40% |
| **TalkBack** | Android | Chrome | ~10% |
| **Narrator** | Windows | Edge | ~4% |
### 2. Testing Priority
```
Minimum Coverage:
1. NVDA + Firefox (Windows)
2. VoiceOver + Safari (macOS)
3. VoiceOver + Safari (iOS)
Comprehensive Coverage:
+ JAWS + Chrome (Windows)
+ TalkBack + Chrome (Android)
+ Narrator + Edge (Windows)
```
### 3. Screen Reader Modes
| Mode | Purpose | When Used |
| ------------------ | ---------------------- | ----------------- |
| **Browse/Virtual** | Read content | Default reading |
| **Focus/Forms** | Interact with controls | Filling forms |
| **Application** | Custom widgets | ARIA applications |
## VoiceOver (macOS)
### Setup
```
Enable: System Preferences → Accessibility → VoiceOver
Toggle: Cmd + F5
Quick Toggle: Triple-press Touch ID
```
### Essential Commands
```
Navigation:
VO = Ctrl + Option (VoiceOver modifier)
VO + Right Arrow Next element
VO + Left Arrow Previous element
VO + Shift + Down Enter group
VO + Shift + Up Exit group
Reading:
VO + A Read all from cursor
Ctrl Stop speaking
VO + B Read current paragraph
Interaction:
VO + Space Activate element
VO + Shift + M Open menu
Tab Next focusable element
Shift + Tab Previous focusable element
Rotor (VO + U):
Navigate by: Headings, Links, Forms, Landmarks
Left/Right Arrow Change rotor category
Up/Down Arrow Navigate within category
Enter Go to item
Web Specific:
VO + Cmd + H Next heading
VO + Cmd + J Next form control
VO + Cmd + L Next link
VO + Cmd + T Next table
```
### Testing Checklist
```markdown
## VoiceOver Testing Checklist
### Page Load
- [ ] Page title announced
- [ ] Main landmark found
- [ ] Skip link works
### Navigation
- [ ] All headings discoverable via rotor
- [ ] Heading levels logical (H1 → H2 → H3)
- [ ] Landmarks properly labeled
- [ ] Skip links functional
### Links & Buttons
- [ ] Link purpose clear
- [ ] Button actions described
- [ ] New window/tab announced
### Forms
- [ ] All labels read with inputs
- [ ] Required fields announced
- [ ] Error messages read
- [ ] Instructions available
- [ ] Focus moves to errors
### Dynamic Content
- [ ] Alerts announced immediately
- [ ] Loading states communicated
- [ ] Content updates announced
- [ ] Modals trap focus correctly
### Tables
- [ ] Headers associated with cells
- [ ] Table navigation works
- [ ] Complex tables have captions
```
### Common Issues & Fixes
```html
<!-- Issue: Button not announcing purpose -->
<button><svg>...</svg></button>
<!-- Fix -->
<button aria-label="Close dialog"><svg aria-hidden="true">...</svg></button>
<!-- Issue: Dynamic content not announced -->
<div id="results">New results loaded</div>
<!-- Fix -->
<div id="results" role="status" aria-live="polite">New results loaded</div>
<!-- Issue: Form error not read -->
<input type="email" />
<span class="error">Invalid email</span>
<!-- Fix -->
<input type="email" aria-invalid="true" aria-describedby="email-error" />
<span id="email-error" role="alert">Invalid email</span>
```
## NVDA (Windows)
### Setup
```
Download: nvaccess.org
Start: Ctrl + Alt + N
Stop: Insert + Q
```
### Essential Commands
```
Navigation:
Insert = NVDA modifier
Down Arrow Next line
Up Arrow Previous line
Tab Next focusable
Shift + Tab Previous focusable
Reading:
NVDA + Down Arrow Say all
Ctrl Stop speech
NVDA + Up Arrow Current line
Headings:
H Next heading
Shift + H Previous heading
1-6 Heading level 1-6
Forms:
F Next form field
B Next button
E Next edit field
X Next checkbox
C Next combo box
Links:
K Next link
U Next unvisited link
V Next visited link
Landmarks:
D Next landmark
Shift + D Previous landmark
Tables:
T Next table
Ctrl + Alt + Arrows Navigate cells
Elements List (NVDA + F7):
Shows all links, headings, form fields, landmarks
```
### Browse vs Focus Mode
```
NVDA automatically switches modes:
- Browse Mode: Arrow keys navigate content
- Focus Mode: Arrow keys control interactive elements
Manual switch: NVDA + Space
Watch for:
- "Browse mode" announcement when navigating
- "Focus mode" when entering form fields
- Application role forces forms mode
```
### Testing Script
```markdown
## NVDA Test Script
### Initial Load
1. Navigate to page
2. Let page finish loading
3. Press Insert + Down to read all
4. Note: Page title, main content identified?
### Landmark Navigation
1. Press D repeatedly
2. Check: All main areas reachable?
3. Check: Landmarks properly labeled?
### Heading Navigation
1. Press Insert + F7 → Headings
2. Check: Logical heading structure?
3. Press H to navigate headings
4. Check: All sections discoverable?
### Form Testing
1. Press F to find first form field
2. Check: Label read?
3. Fill in invalid data
4. Submit form
5. Check: Errors announced?
6. Check: Focus moved to error?
### Interactive Elements
1. Tab through all interactive elements
2. Check: Each announces role and state
3. Activate buttons with Enter/Space
4. Check: Result announced?
### Dynamic Content
1. Trigger content update
2. Check: Change announced?
3. Open modal
4. Check: Focus trapped?
5. Close modal
6. Check: Focus returns?
```
## JAWS (Windows)
### Essential Commands
```
Start: Desktop shortcut or Ctrl + Alt + J
Virtual Cursor: Auto-enabled in browsers
Navigation:
Arrow keys Navigate content
Tab Next focusable
Insert + Down Read all
Ctrl Stop speech
Quick Keys:
H Next heading
T Next table
F Next form field
B Next button
G Next graphic
L Next list
; Next landmark
Forms Mode:
Enter Enter forms mode
Numpad + Exit forms mode
F5 List form fields
Lists:
Insert + F7 Link list
Insert + F6 Heading list
Insert + F5 Form field list
Tables:
Ctrl + Alt + Arrows Table navigation
```
## TalkBack (Android)
### Setup
```
Enable: Settings → Accessibility → TalkBack
Toggle: Hold both volume buttons 3 seconds
```
### Gestures
```
Explore: Drag finger across screen
Next: Swipe right
Previous: Swipe left
Activate: Double tap
Scroll: Two finger swipe
Reading Controls (swipe up then right):
- Headings
- Links
- Controls
- Characters
- Words
- Lines
- Paragraphs
```
## Common Test Scenarios
### 1. Modal Dialog
```html
<!-- Accessible modal structure -->
<div
role="dialog"
aria-modal="true"
aria-labelledby="dialog-title"
aria-describedby="dialog-desc"
>
<h2 id="dialog-title">Confirm Delete</h2>
<p id="dialog-desc">This action cannot be undone.</p>
<button>Cancel</button>
<button>Delete</button>
</div>
```
```javascript
// Focus management
function openModal(modal) {
// Store last focused element
lastFocus = document.activeElement;
// Move focus to modal
modal.querySelector("h2").focus();
// Trap focus
modal.addEventListener("keydown", trapFocus);
}
function closeModal(modal) {
// Return focus
lastFocus.focus();
}
function trapFocus(e) {
if (e.key === "Tab") {
const focusable = modal.querySelectorAll(
'button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])',
);
const first = focusable[0];
const last = focusable[focusable.length - 1];
if (e.shiftKey && document.activeElement === first) {
last.focus();
e.preventDefault();
} else if (!e.shiftKey && document.activeElement === last) {
first.focus();
e.preventDefault();
}
}
if (e.key === "Escape") {
closeModal(modal);
}
}
```
### 2. Live Regions
```html
<!-- Status messages (polite) -->
<div role="status" aria-live="polite" aria-atomic="true">
<!-- Content updates will be announced after current speech -->
</div>
<!-- Alerts (assertive) -->
<div role="alert" aria-live="assertive">
<!-- Content updates interrupt current speech -->
</div>
<!-- Progress updates -->
<div
role="progressbar"
aria-valuenow="75"
aria-valuemin="0"
aria-valuemax="100"
aria-label="Upload progress"
></div>
<!-- Log (additions only) -->
<div role="log" aria-live="polite" aria-relevant="additions">
<!-- New messages announced, removals not -->
</div>
```
### 3. Tab Interface
```html
<div role="tablist" aria-label="Product information">
<button role="tab" id="tab-1" aria-selected="true" aria-controls="panel-1">
Description
</button>
<button
role="tab"
id="tab-2"
aria-selected="false"
aria-controls="panel-2"
tabindex="-1"
>
Reviews
</button>
</div>
<div role="tabpanel" id="panel-1" aria-labelledby="tab-1">
Product description content...
</div>
<div role="tabpanel" id="panel-2" aria-labelledby="tab-2" hidden>
Reviews content...
</div>
```
```javascript
// Tab keyboard navigation
tablist.addEventListener("keydown", (e) => {
const tabs = [...tablist.querySelectorAll('[role="tab"]')];
const index = tabs.indexOf(document.activeElement);
let newIndex;
switch (e.key) {
case "ArrowRight":
newIndex = (index + 1) % tabs.length;
break;
case "ArrowLeft":
newIndex = (index - 1 + tabs.length) % tabs.length;
break;
case "Home":
newIndex = 0;
break;
case "End":
newIndex = tabs.length - 1;
break;
default:
return;
}
tabs[newIndex].focus();
activateTab(tabs[newIndex]);
e.preventDefault();
});
```
## Debugging Tips
```javascript
// Log what screen reader sees
function logAccessibleName(element) {
const computed = window.getComputedStyle(element);
console.log({
role: element.getAttribute("role") || element.tagName,
name:
element.getAttribute("aria-label") ||
element.getAttribute("aria-labelledby") ||
element.textContent,
state: {
expanded: element.getAttribute("aria-expanded"),
selected: element.getAttribute("aria-selected"),
checked: element.getAttribute("aria-checked"),
disabled: element.disabled,
},
visible: computed.display !== "none" && computed.visibility !== "hidden",
});
}
```
## Best Practices
### Do's
- **Test with actual screen readers** - Not just simulators
- **Use semantic HTML first** - ARIA is supplemental
- **Test in browse and focus modes** - Different experiences
- **Verify focus management** - Especially for SPAs
- **Test keyboard only first** - Foundation for SR testing
### Don'ts
- **Don't assume one SR is enough** - Test multiple
- **Don't ignore mobile** - Growing user base
- **Don't test only happy path** - Test error states
- **Don't skip dynamic content** - Most common issues
- **Don't rely on visual testing** - Different experience
## Resources
- [VoiceOver User Guide](https://support.apple.com/guide/voiceover/welcome/mac)
- [NVDA User Guide](https://www.nvaccess.org/files/nvda/documentation/userGuide.html)
- [JAWS Documentation](https://support.freedomscientific.com/Products/Blindness/JAWS)
- [WebAIM Screen Reader Survey](https://webaim.org/projects/screenreadersurvey/)
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