Learn Headless Browsers
A headless browser is a web browser without a graphical user interface.
Headless browsers provide automated control of a web page in an environment similar to popular web browsers, but are executed via a command line interface or using network communication. They are particularly useful for testing web pages as they are able to render and understand HTML the same way a browser would, including styling elements such as page layout, color, font selection and execution of JavaScript and AJAX which are usually not available when using other testing methods. Google stated in 2009 that using a headless browser could help their search engine index content from websites that use AJAX.
- Getting Started with Headless Chrome [readme]
NOTES:
PhantomJS is no longer maintained, Headless Chrome steps in.