Lighthouse is Google’s open-source auditing tool, built into Chrome DevTools, that scores a page across performance, SEO, best practices, and accessibility. Its accessibility audit runs a set of automated checks, largely powered by the same axe-core engine used elsewhere in the industry, and produces a single numeric score along with a list of failed checks.
That score is useful as a quick, repeatable signal, especially in continuous integration pipelines, but a high Lighthouse accessibility score does not mean a site is actually accessible, since it only evaluates what can be checked automatically and misses the majority of real-world WCAG failures.