Nightwatch.js is an integrated, easy-to-use automated testing framework for web applications and websites, written in Node.js. It simplifies end-to-end testing with a clean syntax and built-in command and assertion libraries. Nightwatch supports cross-browser testing across Chrome, Firefox, Safari, and Edge, either locally or on cloud testing services like Sauce Labs and BrowserStack. Its feature-rich API streamlines test creation, execution, and reporting, ensuring reliable and scalable web application quality assurance.