Siteimprove vs Pa11y
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
Quote on request
Quote onlyFree and open source
Open sourceWhat drives the bill
The metric that actually scales your invoice.
Enterprise annual contracts priced by pages crawled and modules.
Free and open source. You pay in engineering time and CI minutes.
Free tier
Free browser extension for single-page checks.
Everything, self-hosted
Open source
LGPL-3.0
Self-hostable
No-code authoring
Languages
Platforms
Fits teams
Adoption
Widely used
Siteimprove · since 2003
Established
OSS community · since 2013
Strengths
- 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.
- 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.
Limitations
- 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.
- No guided manual testing or remediation workflow.
- Testing authenticated or interactive states requires scripting actions.
- Maintenance activity has been intermittent.
Best for
Universities, government and large content organisations with legal accessibility obligations.
Teams wanting free automated accessibility gates across many pages.
Pricing last reviewed August 2026 and is indicative only — confirm on each vendor’s own page.