Pa11y

An open-source automated accessibility testing tool that runs from the command line and in continuous-integration pipelines. Pa11y can drive either axe-core or HTML CodeSniffer as its underlying rule engine, returning JSON-formatted results classified by severity (critical, serious, moderate, minor) and mapped to WCAG success criteria. It is widely used in accessibility research and engineering workflows for crawling and auditing many pages of a site in batch, though like all automated tools it covers only a subset of WCAG criteria (roughly 50%) and cannot replace manual evaluation.