User testing is an important aspect of the development process of any web project, that's why headless browsers can be great for automating and testing web pages programmatically, PhantomJS is one of many headless browsers basicaly a WebKit browser with JavaScript API, which means that the rendered web pages are never actually displayed, just because it is a browser but without a GUI.




$ sudo add-apt-repository ppa:chris-lea/node.js
$ sudo apt-get update
$ sudo apt-get install nodejs
$ sudo npm install -g phantomjs


$ brew install node
$ curl | sh
$ npm install -g phantomjs

Now you should now have PhantomJS installed, you check that by running : $ phantomjs --version

PhantomJS is very powerfull tool, it lets you manipulate pages, access page settings(prevent loading images, prevent running Javascript), accessing the filesystem, running Javascript and you can capture webpage, it can be coupled with other testing frameworks(like QUnitJS)

Testing your responsive design

PhantomJS can capture the content of any webpage in PNG, JPEG, GIF or PDF file, it let's you set the viewport size, the zoom factor, the user-agent and more usefull stuff.

    requires: phantomjs, async
    usage: phantomjs capture.js
var async = require('async'),
    sizes = [
        [320, 480],
        [320, 568],
        [600, 1024],
        [1024, 768],
        [1280, 800],
        [1440, 900]

function capture(sizes, callback) {
    var page = require('webpage').create();
    page.viewportSize = {
        width: sizes[0],
        height: sizes[1]
    page.zoomFactor = 1;'', function (status) {
        var filename = sizes[0] + 'x' + sizes[1] + '.png';
        page.render('./screenshots/' + filename);

async.eachSeries(sizes, capture, function (e) {
    if (e) console.log(e);

I have coupled PhantomJS with async.js so i can take multiple screenshots, now all you need to do is to run phantomjs capture.js from the commandline, the good part is that PhantomJS will capture all the page not only the viewport.

Responsive Design Screenshots

UPDATE 14/07/2013 : The script also works with SlimerJS, SlimerJS is similar to PhantomJs, except that it runs Gecko, the browser engine of Mozilla Firefox, instead of Webkit.

Mentioned on

  • Envato - Techniques for mobile and responsive cross-browser testing.