Selenium Components

The Four Main Components

• Selenium IDE: a browser extension for recording and playing back simple tests.
• Selenium WebDriver: the core API for programmatically automating browsers.
• Selenium Grid: distributes test execution across multiple machines and browsers in parallel.
• Selenium RC (legacy): the original automation tool, now largely replaced by WebDriver.

How They Fit Together

IDE is useful for quick prototyping, WebDriver is the workhorse for real automation scripts, and Grid scales that automation across many browsers and machines simultaneously.