Automated Accessibility Scanning: How It Works

Automated accessibility scanning has become an indispensable tool for organizations wanting to achieve and maintain WCAG compliance. But what actually happens under the hood?

In this guide, we explain how automated scanners work, which problems they find (and miss), and how to implement them in your development process.

Understanding the technology helps you use tools effectively and avoid common misconceptions like 'automated scanning is enough for compliance'.

What is automated scanning?

Automated accessibility scanning means a program systematically analyzes web pages against defined accessibility criteria (usually WCAG).

How it differs from manual testing:

Types of automated scanning:

How the technology works

An accessibility scanner works in several steps:

1. Crawling

Scanner starts at a URL and follows links to discover all pages. Advanced scanners handle JavaScript-rendered content and single-page applications.

2. DOM analysis

For each page, HTML structure is parsed. Scanner builds a representation of the accessibility tree – the same structure assistive technology uses.

3. Rule checking

Each element is tested against a rule set based on WCAG. Common checks:

4. Reporting

Findings are categorized by severity, WCAG criterion, and page location. Modern tools suggest remediation.

Technology behind it:

Most tools use axe-core (Deque's open source engine) or similar. Xrayd combines axe-core with proprietary rules and AI-assisted analysis for deeper insights.

What it finds and misses

Automated scanning finds (good at):

Automated scanning misses (bad at):

Statistics:

Studies show automated tools find 30-40% of WCAG violations. That's significant – but means the majority requires human judgment.

Automation is your baseline defense, not your only strategy. It finds the obvious problems so you can focus manual testing on the complex ones.

Choosing the right tool

Factors to consider:

Coverage:

How many pages need scanning? Individual pages or entire site? SPA support?

Integration:

Need to integrate with CI/CD? Jira? Slack?

Reporting:

Need reports for management? Export formats?

Cost:

Free tools (Lighthouse, Pa11y) vs. paid (Xrayd, Siteimprove)

Xrayd as example:

Xrayd scans entire sites, schedules automatically, integrates with Slack/Jira, and generates reports tailored for different audiences. AI-assisted analysis helps prioritize and understand issues.

Recommendation:

For individual developers: Lighthouse + axe DevTools (free). For teams and agencies: Xrayd or similar platform for automation and overview.

Implement in your process

1. CI/CD integration

Run automated tests with every pull request. Set thresholds – e.g., 'no critical issues allowed'.

2. Scheduled monitoring

Run daily or weekly scans. Catch problems introduced via CMS content, third-party scripts, or A/B tests.

3. Alerting

Set up alerts for critical issues. Send to Slack or email. Include responsible person.

4. Reporting

Generate monthly reports for management. Show trends over time. Celebrate progress!

5. Integration with issue tracking

Automatically create Jira tickets for new issues. Link to relevant developer.

Example workflow: