Compare software

Total ValidatorSiteOne Crawler
Freemium

A Basic edition is offered alongside paid Pro and CI editions.

 Free

Free and open source.

Browser extension Windows, macOS, Linux, Command line
  • Accessibility tests for WCAG 2.2, Section 508 and ARIA
  • HTML, CSS, link and spelling checks in one tool
  • Broad audit covering SEO, security, accessibility and performance
  • Both a desktop GUI and a scriptable CLI
  • Advanced features are split across paid editions
  • Supported operating systems are not stated on the homepage
  • The large number of CLI options takes time to learn
  • Crawling large sites can put load on the target server
Downloadable app, Browser extension Downloadable app
Closed source Open source
License not stated License not stated
Not stated if an account is needed No account needed
Not stated if it works offline Not stated if it works offline

Checked October 2, 2026

Checked September 24, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.