81 lines
2.8 KiB
Markdown
81 lines
2.8 KiB
Markdown
# Severity Rubric
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## Core Principle
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**Severity = Impact x Likelihood**, NOT WCAG conformance level.
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- Level A vs AA is a *conformance tier*, not a risk rating
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- A Level A failure can be LOW severity (decorative image missing alt)
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- A Level AA failure can be CRITICAL (focus outline removed)
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## Severity Levels
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### Critical
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- **Description**: Completely blocks access for users with disabilities
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- **Impact**: Prevents task completion
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- **Examples**:
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- Keyboard trap preventing navigation (2.1.2, Level A)
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- Missing alt text on primary action image (1.1.1, Level A)
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- Form submission inaccessible via keyboard (2.1.1, Level A)
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- Focus outline removed from focusable elements (2.4.7, Level AA)
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### High
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- **Description**: Significantly degrades experience or blocks common workflows
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- **Impact**: Makes tasks difficult or requires workarounds
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- **Examples**:
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- No skip navigation on complex site (2.4.1, Level A)
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- Poor contrast on primary CTA button (1.4.3, Level AA)
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- Missing error suggestions on required form (3.3.3, Level AA)
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- Touch targets too small on mobile (2.5.8, Level AA)
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### Medium
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- **Description**: Minor usability impact, affects subset of users
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- **Impact**: Causes confusion or requires extra effort
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- **Examples**:
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- Decorative icon not hidden but in acceptable context (1.1.1, Level A)
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- Link text needs slight improvement for clarity (2.4.4, Level A)
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- Missing autocomplete on optional field (1.3.5, Level AA)
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### Low
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- **Description**: Best practice enhancement, minimal user impact
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- **Impact**: Nice-to-have improvement
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- **Examples**:
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- Could add tooltips for better UX (not required)
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- Page title could be more descriptive (2.4.2, Level A - but functional)
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## Calculation Guide
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### Impact Assessment
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| Level | Description | Severity Modifier |
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|-------|-------------|-------------------|
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| Blocker | Prevents access | Critical/High |
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| Degraded | Makes difficult | High/Medium |
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| Friction | Adds effort | Medium/Low |
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| Minor | Barely noticeable | Low |
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### Likelihood Assessment
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| Level | Description | Severity Modifier |
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|-------|-------------|-------------------|
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| Core flow | All users hit it | Increase severity |
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| Common | Many users hit it | Base severity |
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| Edge case | Few users hit it | Decrease severity |
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| Rare | Almost never | Low |
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## Examples
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### Same Criterion, Different Severity
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**Missing alt text (1.1.1, Level A)**:
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- Hero image: Impact=Blocker, Likelihood=All users → **CRITICAL**
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- Decorative footer icon: Impact=Minor, Likelihood=Rare → **LOW**
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**No skip link (2.4.1, Level A)**:
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- 3-item navigation: Impact=Friction, Likelihood=Common → **MEDIUM**
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- 50-item navigation: Impact=Degraded, Likelihood=All users → **HIGH**
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**Poor contrast (1.4.3, Level AA)**:
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- Primary CTA button: **CRITICAL**
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- Body text: **HIGH**
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- Footer link: **MEDIUM**
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- Decorative text: **LOW**
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