Pa11y vs Siteimprove
Feature checklists rarely decide anything. What decides it is the pricing metric, who has to write the tests, and which limitation you can live with.
Entry price
Free and open source
Open sourceQuote on request
Quote onlyWhat drives the bill
The metric that actually scales your invoice.
Free and open source. You pay in engineering time and CI minutes.
Enterprise annual contracts priced by pages crawled and modules.
Free tier
Everything, self-hosted
Free browser extension for single-page checks.
Open source
LGPL-3.0
Self-hostable
No-code authoring
Languages
Platforms
Fits teams
Adoption
Established
OSS community · since 2013
Widely used
Siteimprove · since 2003
Strengths
- Free, scriptable and trivially added as a CI gate.
- Tests a sitemap of URLs in one run, unlike page-by-page extensions.
- Self-hosted dashboard for tracking without a vendor.
- Scans entire large sites and assigns findings to content owners, not just developers.
- Combines accessibility with SEO and content quality in one governance view.
- Reporting suited to demonstrating compliance progress to executives and regulators.
Limitations
- No guided manual testing or remediation workflow.
- Testing authenticated or interactive states requires scripting actions.
- Maintenance activity has been intermittent.
- Expensive and aimed at organisations with a governance function.
- Weak fit for application testing as opposed to content sites.
- Limited shift-left developer tooling compared to Deque.
Best for
Teams wanting free automated accessibility gates across many pages.
Universities, government and large content organisations with legal accessibility obligations.
Pricing last reviewed August 2026 and is indicative only — confirm on each vendor’s own page.