No. Automated scans cannot replace an accessibility audit. Scans detect approximately 25% of accessibility issues by evaluating HTML, CSS, and ARIA attributes against Web Content Accessibility Guidelines (WCAG) success criteria. The remaining 75% of issues require human evaluation, which is what an audit provides.
| Key Point | What It Means |
|---|---|
| Scan Coverage | Approximately 25% of WCAG issues are detectable by automated scans |
| Audit Coverage | An audit evaluates all applicable WCAG criteria through human review |
| What Scans Do Well | Flag code-level patterns like missing form labels or empty link text |
| What Scans Cannot Do | Evaluate context, meaning, reading order, or screen reader experience |
What Automated Scans Actually Detect
Scans load a web page and conduct programmatic checks against a set of WCAG success criteria. They are effective at identifying issues that exist in code: missing alternative text attributes, empty buttons, duplicate IDs, and form fields without associated labels.
These are real issues, and scans identify them quickly across large numbers of pages. For organizations with hundreds or thousands of pages, scans are the only practical way to flag code-level patterns at scale.
What Falls Outside Scan Coverage
The 75% of issues that scans miss are the ones that require human judgment. A scan can confirm that an image has an alt attribute, but it cannot determine whether the text in that attribute accurately describes the image. A scan can detect that a heading element exists, but it cannot evaluate whether the heading structure makes logical sense to someone using a screen reader.
Keyboard operability, focus management, screen reader announcements, and the overall experience for people using assistive technology all require a person to evaluate. No automated tool can assess these interactions.
How Scans and Audits Work Together
Scans and audits serve different functions in an accessibility program. Scans provide ongoing monitoring. They can run on recurring schedules (daily, weekly, or monthly) and track whether new code-level issues appear over time.
An audit is a point-in-time evaluation conducted by an accessibility professional. It includes screen reader testing, keyboard testing, visual inspection, and code review. The audit identifies the full range of WCAG conformance issues across a defined scope of pages or screens.
Most organizations use both. Scans provide continuous visibility into the 25% of issues they can detect. Audits provide the thorough evaluation that covers everything else.
Why Scans Alone Create a False Sense of Conformance
A clean scan result does not mean a site conforms to WCAG. It means the site passed the automated checks, which represent a quarter of the full picture. Organizations that rely only on scans often believe their site is accessible when significant issues remain undetected.
This gap becomes especially relevant in procurement and legal contexts, where WCAG 2.1 AA conformance is the referenced standard. A scan report does not substitute for an Accessibility Conformance Report (ACR) or a professional evaluation.
Scans are a valuable and necessary part of accessibility work. They are not a replacement for the human evaluation that an audit provides.