Free accessibility scan tools and paid scan tools both check pages against WCAG success criteria, but they serve different purposes. Free tools work well for spot checks on individual pages and quick developer feedback. Paid tools add scheduled monitoring, authenticated page access, multi-site dashboards, role-based access, and reporting features built for teams managing accessibility across many properties. Both tiers detect roughly the same share of issues, since scans only flag approximately 25% of issues regardless of price.
| Factor | What It Means |
|---|---|
| Detection rate | Both tiers detect approximately 25% of WCAG issues. Price does not change scan coverage. |
| Page volume | Free tools typically scan one page at a time. Paid tools scan entire sites and portfolios on a schedule. |
| Authenticated pages | Free tools rarely scan behind logins. Paid tools support authenticated session scanning. |
| Reporting | Free tools output a single page report. Paid tools provide trend data, exports, and team dashboards. |
| Best fit | Free for developers and one-off checks. Paid for ongoing programs across multiple properties. |
What Free Scan Tools Cover
Free accessibility scan tools come in several formats: browser extensions, web-based scanners that accept a URL, and open source command-line packages developers can run locally. Each loads a page, parses the HTML, CSS, and ARIA attributes, and reports automatable issues against WCAG success criteria.
The output is usually a list of issues with the related success criterion, the offending element, and a short description. Most free tools target a single page per scan. Some browser extensions can evaluate the current tab, including pages behind a login the user is already viewing, but they do not crawl or save results across sessions.
Free tools work well for developers checking a build, designers validating a prototype, or anyone confirming that a specific page renders without obvious automatable issues. They are also useful for sampling: pulling five or ten pages to get a general sense of where a site stands before committing to a deeper evaluation.
What Paid Scan Tools Add
Paid scan tools use the same kind of checks under the hood. The difference is the infrastructure built around the scan engine. Paid platforms include site-wide crawling, scheduled scans (daily, weekly, monthly, or custom), authenticated page scanning through browser extensions or session capture, and dashboards that aggregate results across many sites.
Reporting becomes the major separator. Paid tools track issue counts over time, show whether remediation work is reducing open issues, support exports for engineering teams, and let multiple users assign or comment on findings. Some paid platforms add issue prioritization based on user impact and risk factor scoring, so teams can sequence work without manually triaging hundreds of flags.
Paid tools also tend to support team workflows: role-based access, project grouping, and integrations with issue trackers used by product and engineering teams. For an organization managing one marketing site, this is overkill. For an organization managing fifty properties, it is the entire point.
Where Free and Paid Are Equal
Detection coverage. Both tiers run automated checks that catch roughly a quarter of WCAG issues. The remaining issues, which include most keyboard interaction problems, screen reader output quality, focus management on dynamic components, meaningful sequence, and the accuracy of accessible names, require human evaluation. No scan tool, free or paid, identifies these reliably.
This is the part that catches buyers off guard. Paying more does not buy more coverage of the WCAG. It buys scale, scheduling, and reporting around the same automated layer.
Choosing Between Free and Paid
The decision comes down to volume, frequency, and program maturity. Use free tools when:
- Page count is small: a handful of pages where one-off scans are practical
- Audience is technical: developers reading raw output and acting on it
- Scope is limited: spot checks during development, not ongoing program tracking
- No team coordination is needed: one person reviews and acts on results
Move to paid tools when scans need to run on a schedule, results need to be visible to multiple team members, authenticated areas need coverage, or trend data matters for reporting up to leadership. Paid tools also make sense when scan output feeds into a broader conformance program that includes audits, remediation tracking, and conformance reporting.
What Neither Tier Replaces
Whether the scan is free or paid, it covers about 25% of WCAG conformance. The remaining 75% comes from an audit conducted by accessibility professionals using screen reader testing, keyboard testing, visual inspection, and code inspection. A scan identifies the surface layer. The audit identifies issues that affect how people actually use the site.
The most effective accessibility programs pair scans with audits: scans for ongoing monitoring and regression detection, audits for periodic deep evaluation. Free or paid, a scan tool is one input into that program, not the program itself.