Accessibility scans are automated evaluations that crawl through your web pages and flag coded issues that violate WCAG criteria. They run programmatic checks against your HTML, CSS, and ARIA attributes, then produce a report listing each issue by type, location, and severity. Scans are fast, repeatable, and useful for catching patterns across large sites, but they only flag approximately 25% of accessibility issues.
That 25% matters. It means scans are a starting point, not a finish line. The remaining issues require human evaluation to identify. Still, scans play a real role in any accessibility workflow when you understand what they do and where they stop.
What Happens During an Accessibility Scan?
A scan engine visits each page in your defined scope and parses the DOM. It checks elements against a rules library mapped to WCAG success criteria. Each rule corresponds to something the code can answer with certainty: Does this image have an alt attribute? Does this form input have a label? Is there sufficient color contrast between foreground and background text?
When a rule is violated, the scan logs the issue with the relevant HTML snippet, the WCAG criterion it maps to, and typically a severity rating. Some tools also flag "needs review" items, which are potential issues the scan cannot confirm programmatically.
| Scan Characteristic | What to Know |
|---|---|
| Coverage | Scans flag approximately 25% of WCAG issues |
| Speed | Results returned in minutes, even for large sites |
| Best Use | Catching code-level patterns like missing alt text, empty links, and contrast ratios |
| Primary Limitation | Cannot evaluate context, meaning, or usability for assistive technology users |
| Role in Conformance | Supports ongoing monitoring but does not determine WCAG conformance |
What Can Scans Detect?
Scans are strongest with binary, code-verifiable checks. If the answer is yes or no based purely on the markup, a scan can catch it.
Common issues scans identify include missing alternative text on images, empty link text, missing form labels, improper heading hierarchy, and color contrast below WCAG AA thresholds. These are valuable catches. A single missing form label repeated across 200 pages is the kind of pattern scanning was built for.
Scans also identify duplicate IDs, missing document language declarations, and certain ARIA misuses where attributes are applied to incompatible elements.
What Scans Cannot Do
A scan cannot tell you if an image's alt text is accurate. It can confirm the attribute exists, but whether "blue shirt" actually describes a photo of a product return policy flowchart is a question only a human can answer.
Keyboard navigation is another area scans miss. Whether a user can tab through a modal dialog, close it, and return focus to the trigger element requires someone to interact with the page. The same applies to screen reader compatibility, logical reading order, and whether custom components communicate their state to assistive technology.
This is why scans flag approximately 25% of issues. The remaining 75% lives in context, meaning, interaction, and user experience, all of which require human evaluation.
How Does Scanning Fit Into a WCAG Conformance Workflow?
Scans serve two primary functions: initial baseline detection and ongoing monitoring.
At the start of a project, conducting a scan gives your team a quick view of code-level issues across your digital asset. This is useful for understanding the scope of work before deeper evaluation begins. After remediation, regular scans confirm that previously fixed issues have not regressed and that new content has not introduced fresh code-level problems.
The Accessibility Tracker Platform includes scan and monitoring as a standalone feature. Pages are scanned on a set schedule, and results feed directly into your project dashboard. This keeps monitoring data visible alongside your broader conformance tracking without requiring a separate tool or login.
Scans do not replace the need for a manual accessibility audit. A manual audit is the only way to determine WCAG conformance. But consistent scanning between audits catches regressions early, before they compound.
What Makes One Scan Different From Another?
Not all scan engines are identical. Differences show up in rules coverage, how authenticated pages are managed, and how results are reported.
Some scanners only evaluate publicly accessible pages. Others allow authenticated scanning, which means they can evaluate content behind a login, like dashboards, account settings, or internal tools. If your web app or SaaS product has authenticated states, this distinction matters.
Reporting quality also varies. A scan that dumps 3,000 issues into a flat list with no grouping or prioritization creates more work than it saves. Look for tools that categorize results by page, group repeated issues, and map each finding to its specific WCAG criterion. The Accessibility Tracker Platform organizes scan results by page and category, so your team sees patterns instead of noise.
How Often Should You Run Scans?
For sites with frequent content updates, weekly or biweekly scans are reasonable. For more static sites, monthly scans are typically enough. The goal is to catch regressions before they spread across templates or content types.
Automated monitoring, where scans run on a recurring schedule without manual initiation, is the most reliable approach. It removes the dependency on someone remembering to trigger a scan after each deploy or content update.
Ongoing monitoring is recommended as part of any accessibility maintenance plan, and the Accessibility Tracker Platform makes that monitoring continuous without adding manual overhead to your team's workflow.
Can a scan tell me if my site is WCAG conformant?
No. Scans flag approximately 25% of accessibility issues. WCAG conformance requires full evaluation against all applicable criteria, which can only be determined through a manual accessibility audit conducted by a qualified auditor.
Do scans work on mobile apps?
Most web-based accessibility scanners evaluate web content rendered in a browser. Mobile apps built natively for iOS or Android require different evaluation tools and methods. Web apps accessed through a mobile browser can be scanned like any other web page.
Are scan results useful for ADA compliance?
Scan results are one piece of ADA compliance evidence. They show that your organization is actively monitoring for accessibility issues. But because scans only cover a fraction of WCAG criteria, they cannot serve as standalone proof of compliance. Pair scan monitoring with periodic audits and documented remediation for a stronger compliance position.
What is the difference between a scan and an audit?
A scan is an automated check that evaluates code against a subset of WCAG criteria. An audit is a thorough, human-led evaluation that covers all applicable WCAG success criteria, including those requiring contextual judgment. These are completely separate activities. Scans support ongoing monitoring. Audits determine conformance.
Scans are a practical, repeatable part of accessibility management. They catch what code can tell you and flag regressions before they grow. Knowing where scans stop is what makes them useful instead of misleading.
Contact Accessibility Tracker to set up automated scan monitoring for your web pages.