Am I Responsive? – this is a brilliant tool! You can type the URL you are interested in, click “Go!” button and see the preview of the URL on four different screen sizes – large desktop, medium desktop, tablet, and smartphone. No waiting in queue, no screenshots – all is live, scrollable and instant. There is also a bookmarklet which you can add to your browser and then preview any page with a single click. You can even rearrange the preview screens by dragging them around. And on top of all of that, even the localhost URLs work – the killer feature for any web developer!