Alfa vs Sa11y

Alfa is a free, open accessibility testing engine for websites built with HTML, CSS, and JavaScript. It checks pages against accessibility standards such as WCAG, using included rules or pluggable rules in the ACT Rules Format. Developers can add custom rules and filter results by conformance level or WCAG version. Audit output follows the Evaluation and Report Language schema as JSON-LD, and the command-line interface can audit a single page and save results as JSON. Scraper and crawler tools create page representations and discover pages across a site or subdomain. Ready-made integrations cover frameworks and test tools including Angular, React, Vue, Cypress, Jest, Playwright, Puppeteer, Selenium, and WebdriverIO. Alfa is distributed as separate npm packages under the MIT license. It runs in ECMAScript 2022-compatible JavaScript environments, including recent Node.js and browser versions. Building from source requires Node.js 20 or later and Yarn. The project says most integrations are experimental and may change; older environments may be targetable from source but are not explicitly supported.

Sa11y has no write-up on Specifiction yet; its figures are above.