Clients sometimes ask how an automated scan stacks up against a full accessibility audit, and the answers always points in the same direction. A scan flags approximately 25% of accessibility issues. A (manual) audit is the only way to determine WCAG conformance. That’s the starting point.
The questions below come up in nearly every project intake. Understanding them upfront saves time and removes ambiguity from the scan vs audit decision.
| Client Question | Core Answer |
|---|---|
| Can a scan tell me if my site conforms to WCAG? | No. Scans detect approximately 25% of issues. Conformance requires a (manual) audit. |
| Is a scan enough for ADA compliance? | A scan alone does not establish ADA compliance because it cannot determine WCAG conformance. |
| What does an audit cover that a scan does not? | Keyboard navigation, screen reader behavior, cognitive flow, content structure, and context-dependent criteria. |
| When does a scan make sense? | As a preliminary check between audits or during development to catch surface-level code issues. |
| Do I need both? | They serve separate purposes. An audit determines conformance. A scan monitors for regressions over time. |
Can a Scan Tell Me if My Site Conforms to WCAG?
No. Scans are automated tools that check code against a subset of WCAG criteria. They flag things like missing alt text, empty form labels, and low color contrast ratios. These are real issues worth catching.
But scans cannot evaluate how a screen reader user experiences a multi-step form. They cannot determine whether a custom dropdown is operable by keyboard. They cannot assess whether the reading order of a page makes sense or whether link text communicates purpose in context.
Scans detect approximately 25% of issues. The remaining 75% require human evaluation. WCAG conformance can only be determined through a (manual) accessibility audit.
Is a Scan Enough for ADA Compliance?
ADA compliance depends on WCAG conformance. Since a scan cannot determine conformance, it cannot establish compliance on its own.
Clients in regulated industries or those responding to legal demand letters need documentation that holds up. That documentation comes from an audit conducted by an evaluator, not a scan report. A scan output does not carry the same weight in a legal or procurement context.
What Does an Audit Cover That a Scan Does Not?
An audit evaluates every applicable WCAG criterion across a representative sample of pages and states. The evaluator interacts with the site the way users with disabilities do.
This includes keyboard-only navigation through every interactive component, screen reader evaluation across content types, and assessment of dynamic behaviors like modals, error messages, and live regions. It also covers content structure, heading hierarchy, and whether ARIA attributes are used correctly.
A scan reads the DOM. An audit evaluates the experience.
When Does a Scan Make Sense on Its Own?
Scans work well in two scenarios. The first is during development, where a scan integrated into the build pipeline catches code-level issues before they reach production. The second is between audits, where periodic scans help monitor for regressions introduced by new content or feature updates.
In both cases, the scan serves a maintenance function. It is not a substitute for the audit itself.
Do I Need Both a Scan and an Audit?
They are completely separate activities with different purposes. Clients who treat them as interchangeable end up with gaps in their accessibility program.
An audit provides a conformance baseline. It identifies every issue across the evaluated sample and maps each one to specific WCAG criteria. A scan provides ongoing surface-level monitoring. Used together in sequence, they form a complete picture. Used in isolation, only the audit delivers conformance data.
How Do I Know Which One I Need Right Now?
The answer depends on where you are in your accessibility lifecycle.
If your site or web app has never been professionally evaluated against WCAG, an audit is the starting point. There is no shortcut to establishing a conformance baseline.
If your site was audited within the past year and you want to confirm that recent updates did not introduce new issues, a scan is a reasonable interim step. It will not catch everything, but it can flag obvious regressions.
If you are responding to a legal demand, procurement request, or regulatory deadline, the audit is what produces the documentation you need.
What About Cost?
Scans are less expensive than audits. That is part of why clients ask whether a scan is enough. The cost of an accessibility audit reflects the depth of evaluation involved: an evaluator working through every interactive component, every content type, and every state.
The cost difference is real. So is the gap in what each activity produces. A scan gives you a partial list of code-level issues. An audit gives you a complete conformance assessment with documentation that maps issues to WCAG criteria, priority levels, and remediation guidance.
Accessible.org structures every audit to deliver a clear, actionable report. The value of that output extends well beyond the initial evaluation because it becomes the foundation for remediation, tracking, and ongoing conformance.
Should I get a scan before requesting an audit?
It is not necessary. A scan before an audit can help your development team fix surface-level code issues in advance, which may reduce the total number of issues the audit identifies. But it does not change the scope or purpose of the audit itself. Many clients go directly to the audit.
Can a scan identify issues with screen reader compatibility?
Not meaningfully. Scans can flag missing ARIA labels or empty alt attributes, but they cannot evaluate how a screen reader actually announces and navigates content. That requires a human evaluator using assistive technology.
How often should I repeat an audit?
After significant design changes, feature launches, or platform migrations. If your site content and functionality remain stable, an annual audit is a reasonable cadence. Between audits, scans help catch regressions early.
The scan vs audit decision comes down to what you need the output to do. If you need conformance data, legal documentation, or a remediation roadmap, the audit is the only path. If you need a quick check between evaluations, a scan fills that role.
Contact Kris Rivenburgh to discuss your accessibility project.