Open Source Accessibility Projects: Tools Built by the Community

Open source software plays a critical role in accessibility. Some of the most important testing tools, assistive technologies, and design resources are open source — freely available, community-maintained, and continuously improved. Contributing to these projects builds skills, advances the field, and demonstrates professional competence.

Testing and Evaluation Tools

axe-core (Deque Systems)

Repository: github.com/dequelabs/axe-core Language: JavaScript What it does: The most widely used accessibility testing engine. axe-core evaluates web content against WCAG rules and generates structured results. It powers Deque’s axe browser extension, Lighthouse’s accessibility audits, and integrations in hundreds of development tools.

Why it matters: axe-core’s rule set is maintained by accessibility experts and is the de facto standard for automated web accessibility testing. Contributing to axe-core means improving the tool that millions of websites are tested against.

pa11y

Repository: github.com/pa11y/pa11y Language: JavaScript/Node.js What it does: An automated accessibility testing tool that can be run from the command line, integrated into CI/CD pipelines, or used as a dashboard for monitoring multiple URLs. pa11y supports WCAG 2.1 testing and integrates with axe and HTML_CodeSniffer.

Why it matters: pa11y’s simplicity makes it ideal for integration into automated testing workflows. Its dashboard component (pa11y-dashboard) provides monitoring for organizations tracking accessibility across multiple properties.

HTML_CodeSniffer

Repository: github.com/squizlabs/HTML_CodeSniffer Language: JavaScript What it does: A JavaScript application that checks HTML source code against accessibility standards (WCAG 2.1, Section 508). Can be used as a bookmarklet, integrated into CMS platforms, or run as part of automated testing.

Lighthouse (Google)

Repository: github.com/GoogleChrome/lighthouse Language: JavaScript What it does: An automated tool for improving web page quality, including an accessibility audit that uses axe-core. Built into Chrome DevTools and available as a Node module and CLI tool.

WAVE (WebAIM)

While the WAVE web service itself is not open source, WebAIM provides the WAVE browser extensions for Chrome and Firefox free of charge. The tool provides visual feedback about accessibility issues directly on the page.

Screen Readers

NVDA (NV Access)

Repository: github.com/nvaccess/nvda Language: Python What it does: NonVisual Desktop Access is a free, open source screen reader for Windows. It is the most used free screen reader worldwide and the second most used screen reader overall (after JAWS, which is commercial).

Why it matters: NVDA’s open source nature means that screen reader compatibility can be verified and tested freely. For developers who cannot afford JAWS, NVDA provides a professional-grade testing tool. NV Access, the Australian nonprofit that develops NVDA, accepts donations and sponsorships to sustain development.

Orca (GNOME)

Repository: Part of GNOME project Language: Python What it does: The default screen reader for Linux desktops (GNOME environment). Provides speech and Braille output for Linux applications and web browsers.

Design and Development Resources

Repository: github.com/a11yproject/a11yproject.com What it is: A community-driven resource for web accessibility. The site itself is open source, and contributions are welcome. Resources include checklists, how-to articles, and curated links.

GOV.UK Design System

Repository: github.com/alphagov/govuk-design-system Language: Nunjucks, JavaScript What it does: The UK government’s design system provides accessible, tested UI components. All components are tested with assistive technologies and meet WCAG 2.1 Level AA. The design system is used across UK government services and can be adapted for other projects.

U.S. Web Design System (USWDS)

Repository: github.com/uswds/uswds Language: JavaScript, Sass What it does: The U.S. federal government’s design system provides accessible components and design patterns for federal websites. Components are tested against Section 508 requirements.

Inclusive Design Principles

Repository: github.com/nickhuggins/inclusive-design-principles What it is: A community-maintained set of inclusive design principles with translations into multiple languages. Useful as a reference and advocacy tool.

Contributing to Open Source Accessibility

Contributing to accessibility open source projects provides multiple benefits:

Skill development: Working on real-world accessibility codebases deepens understanding of WCAG implementation, assistive technology interaction, and accessible component patterns.

Portfolio building: Open source contributions demonstrate practical skills to potential employers. For developers and designers seeking accessibility careers, contributions to axe-core, pa11y, or NVDA are concrete evidence of competence.

Community impact: Every bug fixed, rule added, or documentation improved helps the millions of users who depend on these tools.

Professional networking: Open source communities connect contributors with leading practitioners. Many accessibility professionals first met through open source collaboration.

How to Start Contributing

Choose a project aligned with your skills (JavaScript developers: axe-core, pa11y; Python developers: NVDA; writers: A11Y Project).
Start with documentation — many projects have documentation gaps that newcomers can fill.
Look for “good first issue” labels on GitHub — these are intentionally scoped for new contributors.
Test and report bugs — running tools against real websites and reporting issues is valuable even without code contributions.
Join the community — most projects have discussion forums, Slack channels, or mailing lists.

For the organizations behind many of these projects, see universal design communities and organizations.

Key Takeaways

axe-core (Deque) and pa11y are the most important open source accessibility testing tools, used by millions of websites and integrated into major development workflows.
NVDA is the leading free screen reader, essential for accessibility testing on Windows.
Government design systems (GOV.UK, USWDS) provide ready-to-use accessible components.
Contributing to open source accessibility projects builds skills, creates portfolio evidence, and advances the field.

Sources

W3C WAI — Evaluation Tools List: https://www.w3.org/WAI/ER/tools/
W3C — WCAG 2.2: https://www.w3.org/TR/WCAG22/
W3C WAI — ARIA Authoring Practices Guide: https://www.w3.org/WAI/ARIA/apg/
Section508.gov — Testing Tools: https://www.section508.gov/test/