PhantomJS is a headless web browser scriptable with JavaScript, running on Windows, macOS, Linux, and FreeBSD. Utilizing QtWebKit as its back-end, it offers fast and native support for various web standards, including DOM handling, CSS selectors, JSON, Canvas, and SVG. This makes it an optimal solution for tasks such as page automation, screen capture, headless website testing, and network monitoring. For example, a simple script can load a webpage and capture it as an image.