Process

Open-Source Accessibility Tools and Resources

By EZUD Published · Updated

Open-Source Accessibility Tools and Resources

Organizations of any size can build robust accessibility testing and development workflows using open-source tools. While commercial tools like Deque’s axe DevTools Pro and Level Access’s platform offer advanced features, their open-source counterparts cover substantial ground and integrate seamlessly into modern development pipelines.

Automated Testing Tools

axe-core (Deque)

The most widely adopted open-source accessibility testing engine. axe-core runs in the browser and evaluates rendered DOM against WCAG 2.2 rules. It powers dozens of other tools and integrations.

  • Use cases: Browser extension testing, CI/CD integration, unit testing
  • Integrations: axe DevTools browser extension (free version), jest-axe for unit tests, cypress-axe for end-to-end tests, @axe-core/playwright for Playwright
  • Strengths: Low false-positive rate, clear remediation guidance, actively maintained by Deque
  • License: MPL-2.0

Pa11y

A Node.js-based accessibility testing tool that runs from the command line or integrates into CI/CD pipelines. Pa11y can test against WCAG 2.2 Level AA using HTML CodeSniffer or axe-core as its testing engine.

  • Use cases: CI/CD pipeline checks, scheduled monitoring, dashboard integration
  • Variants: Pa11y (single page), Pa11y CI (multiple pages), Pa11y Dashboard (web-based monitoring)
  • Strengths: Simple setup, flexible configuration, supports multiple runners
  • License: LGPL-3.0

Accessibility Insights (Microsoft)

A suite of tools including a browser extension (for Chrome and Edge) and a desktop application for Windows. The browser extension includes automated checks and a guided manual assessment workflow.

  • Use cases: Developer testing, guided manual audits, color contrast checking
  • Strengths: Step-by-step manual assessment guidance, visual highlighting, export to CSV
  • License: MIT

HTML CodeSniffer

A client-side JavaScript tool that evaluates HTML against WCAG 2.2 and Section 508 standards. It runs as a bookmarklet or can be integrated into testing frameworks.

  • Use cases: Quick page-level checks, integration with Pa11y
  • License: BSD-3-Clause

Linting and Static Analysis

eslint-plugin-jsx-a11y

An ESLint plugin that catches accessibility issues in JSX (React) code during development. It flags missing alt attributes, incorrect ARIA usage, and inaccessible interactive elements.

  • Use cases: React development, code review, CI/CD linting
  • Strengths: Catches issues before code reaches the browser
  • License: MIT

axe Linter (Deque)

A VS Code extension that highlights accessibility issues directly in the code editor. Free for individual use.

Stylelint a11y

A Stylelint plugin that checks CSS for accessibility issues like insufficient font sizes and missing focus styles.

Screen Readers (Free)

NVDA (NV Access)

A free, open-source screen reader for Windows. NVDA is the most widely used free screen reader globally and the second most used screen reader overall (after JAWS), according to WebAIM’s screen reader survey.

  • Use cases: Testing on Windows with Chrome, Firefox, and Edge
  • License: GPL-2.0

Orca

A free screen reader for Linux, included with many Linux distributions.

VoiceOver (Apple)

Built into macOS, iOS, and iPadOS at no additional cost. Not open-source, but free and widely used for testing on Apple platforms.

Color and Contrast Tools

Colour Contrast Analyser (TPGi)

A desktop application that checks color contrast ratios against WCAG 2.2 requirements. Includes an eyedropper tool for sampling colors from any screen content.

  • License: GPL-3.0

Stark (limited free tier)

A Figma, Sketch, and Adobe XD plugin for checking contrast and simulating vision impairments during design.

Development Resources

W3C ARIA Authoring Practices Guide

The definitive reference for implementing accessible custom widgets. Provides keyboard interaction patterns, ARIA attribute specifications, and code examples for tabs, menus, dialogs, comboboxes, and more.

Deque University (selected free courses)

Deque offers several free accessibility courses covering WCAG fundamentals, testing methodology, and accessible development patterns.

WebAIM

Comprehensive articles, tutorials, and evaluation tools including the WAVE web accessibility evaluator and the WebAIM Million (annual analysis of the top million websites for accessibility).

Integrating Tools into Your Workflow

For maximum impact:

  1. In the editor: eslint-plugin-jsx-a11y and axe Linter catch issues as developers type.
  2. In unit tests: jest-axe or testing-library accessibility assertions verify component accessibility.
  3. In CI/CD: Pa11y CI or axe-core integrations gate builds on accessibility compliance.
  4. In manual testing: NVDA, VoiceOver, and Accessibility Insights provide assistive technology verification.
  5. In monitoring: Pa11y Dashboard or custom scripts provide continuous monitoring.

See automated vs. manual testing for guidance on where automated tools fit in a comprehensive testing strategy, and training developers on accessibility for how to build team skills around these tools.

Key Takeaways

  • axe-core, Pa11y, and Accessibility Insights form a robust open-source testing foundation.
  • NVDA and VoiceOver provide free screen reader testing on Windows and Apple platforms.
  • Linting tools catch accessibility issues during coding, before they reach the browser.
  • Layer tools across the workflow: editor, unit tests, CI/CD, manual testing, and monitoring.
  • Open-source tools cover substantial ground but should be supplemented with manual expert testing and user testing.

Sources

More in Process

Inclusive Design Process Guide: Building Accessibility Into Every Stage Guide Continuous Accessibility Monitoring Accessibility in Design Reviews Nothing About Us Without Us: The Principle That Shapes Inclusive Design

View all Process articles →