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.

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

Scan HTML - Run a11y_scanner.py on all templates
Check contrast - Run contrast_checker.py on stylesheets
Triage - Prioritize Level A violations first
Remediate - Fix critical issues (alt text, form labels, headings)
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

Pre-commit - Quick scan of changed HTML files
PR review - Full scan as part of review checklist
Staging audit - Comprehensive scan before release
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

a11y-audit