Supported Web Standards

Since PhantomJS is based on QtWebKit, it basically supports whatever features shipped in the module. For Qt version 4.8, it is equivalent to QtWebKit 2.2, see the its list of all features for more information.

Detecting Features

Using WebKit version and compare it against other WebKit-based browser is not encouraged. The reason is because every WebKit implementation may have varying support due to its architecture of having interface/ abstraction layer.

The best way to find out if a certain feature is supported or not is via feature detection, for example by using a library like Modernizr. The included examples/features.js illustrates the use of Modernizr and dumps all the detected features, both supported and not supported.

Please note that although a certain feature might be supported, there is no really guarantee that it is 100% supported. You still have run your own extensive tests to make sure that the support level is up to what you need.

Irrelevant Features

The following features, due to the nature of PhantomJS, are irrelevant. They may or may not be supported in any future version.

WebGL would require OpenGL-capable system. Since the goal of PhantomJS is to become 100% headless and self-contained, this is not acceptable. Using OpenGL emulation via Mesa can overcome the limitation, but then the performance would degrade.

Video and Audio would require shipping a variety of different codecs implementation.

CSS 3-D Transformation needs a perspective-correct implementation of texture mapping. It can't be implemented with a penalty in performance.

Plugins such as Flash, Silverlight, etc are platform-dependent. They may also require native window handle, something which PhantomJS can not always provide by being headless.

Each of the above feature needs to be evaluated on a case-by-case to see whether it is suitable to be included or not. Until then, do not rely on them.

Not Tested Features

XPath.