Automating parallel testing in Selenium with TestNG offers significant advantages for cross-browser testing by reducing manual effort, improving coverage, and saving time. TestNG facilitates parallel testing through two main methods: setting the "parallel" attribute in the testing.xml file or using a data provider method with parallel attribute set to true. This approach leverages a hub-node architecture where tests are run on a central hub, with execution distributed across various nodes, each configured with different platforms and browsers. While local setups using Selenium Grid can be limited by hardware constraints and setup complexity, cloud-based platforms like LambdaTest provide scalable solutions with access to 3000+ browser combinations, facilitating seamless integration with various tools. These platforms offer enhanced features such as screenshots, console logs, and video recording, which support detailed test analysis. Using DesiredCapabilities and RemoteWebDriver, testers can ensure compatibility across multiple environments, optimizing the testing process in an agile development landscape.