The Responsinator is a dead simple tool for viewing a web page in all of the the most popular screen sizes all at once. This allows you to rapidly test your responsive design.
Using The Responsinator is easy, just go to responsinator.com and enter the URL of the site to test in the upper left corner.
The site will now load on a variety of pseudo-devices that you can browse individually, all on one screen.
Also helpful is that you can interact with each ‘device’ with full site functionality. Click on links, take actions, everything should work which helps you quickly validate a number of screens in a few clicks. You can even get through authentication screens and SSL. As an added bonus, your session cookies from the actual site will carry through for you in most cases when using The Responsinator - which is helpful when you're testing a complex web application.
What’s even more awesome is that you can inspect and edit individual ‘devices’ to adjust the HTML and CSS just as you would be able to on a full web site. This can help you rapidly correct responsive layout issues on the fly without having to go through a bunch of trial and error with the source project.
The Responsinator warns you that the reproduction of the device’s browser is not exact (since a variety of browsers exist on mobile devices), but it should get you the majority of the way there. They also offer some helpful tips to get the best result out of their service on their about page.
Free services like this get me pumped. Any time a group decides to make something available that will save you a truck load of time without asking anything in return is inspiring.
This is just the first post in a new series about the greatest tools we use on a regular basis, so check back for the next installment.