Accessibility Audit

Category: Engineering Domain: Web Accessibility

Overview

The Accessibility Audit skill provides automated scanning of HTML files for WCAG 2.1 compliance violations and color contrast checking against AA/AAA standards. It catches missing alt text, broken heading hierarchies, unlabeled form inputs, and insufficient color contrast early in development.

Clarify First

Before running the audit, confirm these inputs. If any is unknown or vague, ASK — do not assume:

• Target & scope — which HTML files, directory, or CSS to scan (determines what gets checked and the --file/--dir/--css arguments)
• Conformance level — A, AA, or AAA target (sets contrast thresholds and which violations are CRITICAL vs WARNING vs INFO)
• Use context — one-off remediation vs CI gate (drives --strict gating and JSON output)

Stop rule: ask only the 2-3 that most change the output. If the user says "just draft it," proceed and list your assumptions at the top of the artifact.

Quick Start

# Scan HTML for WCAG violations
python scripts/a11y_scanner.py --file index.html

# Scan a directory of HTML files
python scripts/a11y_scanner.py --dir ./src/templates

# Check color contrast
python scripts/contrast_checker.py --foreground "#333333" --background "#ffffff"

# Parse CSS file for contrast issues
python scripts/contrast_checker.py --css styles.css

# JSON output for CI
python scripts/a11y_scanner.py --file index.html --format json

Tools Overview

a11y_scanner.py

Scans HTML files for WCAG 2.1 violations including structural, semantic, and interactive element issues.

Feature	Description
Image alt text	Detects missing or empty alt on non-decorative images
Heading hierarchy	Validates h1-h6 levels are sequential
Form labels	Ensures inputs have associated label elements
ARIA attributes	Checks ARIA usage correctness
Link text	Flags generic text like "click here" or "read more"
Language attribute	Checks for lang on html element
Tab order	Detects positive tabindex values
Landmarks	Validates semantic landmark usage

contrast_checker.py

Checks color contrast ratios against WCAG AA and AAA thresholds.

Feature	Description
Ratio calculation	Computes relative luminance contrast ratio
AA compliance	4.5:1 normal text, 3:1 large text
AAA compliance	7:1 normal text, 4.5:1 large text
CSS parsing	Extracts color/background pairs from CSS
Color suggestions	Recommends nearest compliant color

Workflows

Full Accessibility Audit

1. Scan HTML - Run a11y_scanner.py on all templates
2. Check contrast - Run contrast_checker.py on stylesheets
3. Triage - Prioritize Level A violations first
4. Remediate - Fix critical issues (alt text, form labels, headings)
5. Re-scan - Verify fixes pass all checks

CI Integration

# Gate on Level A violations
python scripts/a11y_scanner.py --dir ./templates --format json --level A --strict

# Check CSS contrast
python scripts/contrast_checker.py --css ./static/css/main.css --format json

Development Workflow

1. Pre-commit - Quick scan of changed HTML files
2. PR review - Full scan as part of review checklist
3. Staging audit - Comprehensive scan before release
4. Monitoring - Regular scheduled audits

Reference Documentation

• WCAG Guidelines - Conformance levels, success criteria, common fixes

Common Patterns Quick Reference

WCAG Levels

Level	Description	Typical Requirement
A	Minimum baseline	Legal compliance
AA	Industry standard	Most regulations, ADA
AAA	Enhanced	Best practice goal

Contrast Ratios

Context	AA	AAA
Normal text (<18pt)	4.5:1	7:1
Large text (>=18pt bold or >=14pt)	3:1	4.5:1
UI components	3:1	3:1

Quick Fixes

Issue	Fix
Missing alt text	<img alt="Description of image">
Skipped heading	Use sequential h1 through h6
No form label	<label for="inputId">Label</label>
Generic link text	Replace "click here" with descriptive text
Missing lang	<html lang="en">
Positive tabindex	Use tabindex="0" or tabindex="-1" only

Severity Mapping

• CRITICAL - WCAG Level A violations
• WARNING - WCAG Level AA violations
• INFO - WCAG Level AAA recommendations