PhantomJS provides a JavaScript API enabling automated navigation, screenshots, user behavior and assertions making it a common tool used to run browser-based unit tests in a headless system like a continuous integration environment.

[4] The logo commonly used to pictorially refer to PhantomJS is a fluorescent blue ghost atop a black background.

PhantomJS became valuable enough that similar projects adopted the API as a standard way of interacting with headless browsers.

SlimerJS provided a PhantomJS-like API, but on top of Mozilla's Gecko browser engine rather than WebKit.

developed a version of YSlow that leverages PhantomJS to gather performance metrics for websites.