What is Headless Browser?

A headless browser is a web browser without a graphical user interface. In other words it is a browser, a piece of software, that access web pages but doesn't show them to any human being. They're actually used to provide the content of web pages to other programs.
PhantomJS –is a headless WebKit scriptable with a JavaScript API. It has fast and native support for various web standards: DOM handling, CSS selector, JSON, Canvas, and SVG. HtmlUnit –is a “GUI-Less browser for Java programs”.

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