How We Calculate Accessibility Scores

Transparent methodology for BFSG compliance testing

Overview

Our platform uses a combination of automated testing and human verification to evaluate websites against BFSG (Barrierefreiheitsstärkungsgesetz) requirements, which mandate WCAG 2.2 Level AA compliance.

🤖 Automated Testing (Baseline Scores)

Tools Used

  • Playwright - Browser automation framework by Microsoft
  • Axe-core - Industry-standard accessibility testing engine by Deque Systems
  • WCAG 2.2 Level AA - Official Web Content Accessibility Guidelines

What Gets Tested

Automated tools can test approximately 40-60% of WCAG criteria, including:

  • ✅ Missing alt text on images
  • ✅ Color contrast ratios (text vs background)
  • ✅ Form field labels and ARIA attributes
  • ✅ Heading hierarchy (H1, H2, H3, etc.)
  • ✅ Keyboard focus indicators
  • ✅ HTML structure and semantic markup
  • ✅ Link text quality

Scoring Methodology

Step 1: Violation Detection

Axe-core scans the webpage and identifies WCAG violations. Each violation has:

  • WCAG Tags - Which guidelines it violates (e.g., "cat.color", "cat.keyboard")
  • Severity Level - Critical, Serious, Moderate, or Minor
  • Affected Elements - Which HTML elements have issues

Step 2: Severity Weighting

Violations are weighted by severity:

  • Critical - 3x weight (blocks access entirely)
  • Serious - 2x weight (major barrier to access)
  • Moderate - 1x weight (causes difficulty)
  • Minor - 0.5x weight (minor inconvenience)

Step 3: Category Mapping

Violations are mapped to 8 disability categories based on WCAG tags:

  • Visual Blind - cat.text-alternatives, cat.structure, cat.aria
  • Visual Low Vision - cat.color, cat.sensory-and-visual-cues
  • Visual Color Blind - cat.color, cat.sensory-and-visual-cues
  • Auditory Deaf - cat.audio-video, cat.time-and-media
  • Auditory Hard of Hearing - cat.audio-video, cat.time-and-media
  • Motor Limited - cat.keyboard, cat.navigation
  • Motor Severe - cat.keyboard, cat.navigation
  • Cognitive - cat.language, cat.forms, cat.parsing

Step 4: Score Calculation

For categories with specific violations found:

Score = (1 - weighted_violations / total_checks) × 100%

For categories without specific tests:

Score = min(85%, overall_pass_rate × 100%)

Note: Capped at 85% to indicate uncertainty when category-specific tests aren't available

Limitations of Automated Testing

Important: Automated tests CANNOT verify:

  • Video caption accuracy and synchronization
  • Actual screen reader experience and navigation flow
  • Audio quality and clarity
  • Keyboard navigation usability (only structure)
  • Content readability and comprehension
  • Time limit reasonableness
  • Error message clarity

This is why human verification is essential!

Human Verification (Authoritative Scores)

Community Testing Process

Community members with lived experience of disabilities test websites and answer 5-8 questions specific to their disability category. Each question is weighted by importance (10-30%).

Question Weighting Examples

Visual Blind Category (7 questions):

  • Alt text for images - 20% (critical)
  • Screen reader navigation - 25% (critical)
  • ARIA labels - 15% (important)
  • Form labels - 15% (important)
  • Heading structure - 10% (helpful)
  • Skip navigation links - 10% (helpful)
  • Meaningful link text - 5% (minor)

Scoring Formula:

Score = (sum of weights for "yes" answers / total weight) × 100%

Example:
- Questions answered "yes": 20% + 25% + 15% + 10% = 70%
- Total possible weight: 100%
- Final score: 70%

Priority System

When both automated and human scores exist for the same category:

  • ✅ Human scores always take precedence (shown without 🤖 badge)
  • 🤖 Automated scores are replaced by human verification
  • Overall score updates to reflect human-verified data

Overall Website Score

The overall score is calculated as the average of all 8 category scores: 

Overall Score = (Sum of all 8 category scores) / 8

Example:
Visual Blind: 85%
Visual Low: 70%
Visual Color: 75%
Auditory Deaf: 85%
Auditory Hard: 85%
Motor Limited: 80%
Motor Severe: 80%
Cognitive: 90%

Overall = (85 + 70 + 75 + 85 + 85 + 80 + 80 + 90) / 8 = 81.25%

Score Interpretation

90-100% - Excellent

BFSG Compliant - Few or no accessibility barriers

70-89% - Good

Minor issues present - Improvements recommended

Below 70% - Poor

Major barriers - Significant work needed

Legal Compliance & Transparency

BFSG Requirements

The Barrierefreiheitsstärkungsgesetz (BFSG) came into effect in June 2025 and requires:

  • Compliance with WCAG 2.2 Level AA standards
  • Accessibility for people with visual, auditory, motor, and cognitive disabilities
  • Applies to e-commerce, banking, telecommunications, transport, and digital content
  • Microenterprises (< 10 employees, < €2M turnover) are exempt

Our Commitment

  • ✅ We use industry-standard tools (Axe-core by Deque Systems)
  • ✅ Scores are based on objective WCAG criteria, not opinions
  • ✅ We're transparent about limitations of automated testing
  • ✅ We prioritize human verification from people with disabilities
  • ✅ All test results are timestamped and auditable
  • ✅ Methodology is publicly documented (this page)

Not Legal Advice

Important Disclaimer: This platform provides accessibility testing as a service. Scores are informational and do not constitute legal compliance certification. We recommend consulting with accessibility experts and legal counsel for official BFSG compliance audits.

Questions About Our Methodology?

We believe in full transparency. If you have concerns or questions about how we calculate scores, please review our open methodology or contact us.

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