Viewport Resizer – Browser Based Tool to Test Any Website’s Responsiveness
http://lab.maltewassermann.com/viewport-resizer/

More than 32k active users access Viewport Resizer in 158 countries! Viewport resizer is a browser-based tool to test any website’s responsiveness. Just save the bookmarklet, go to the page you want to test, click on your created bookmarklet and check all kinds of screen resolutions of the page. The smartest way to share your defined environment of devices and breakpoints directly with your team and client. This bookmarklet should not replace a real device simulation. It rather helps you, your team and client testing statuses, transitions, text length etc. throughout different device types. This has been added to the tools section of Research Resources Subject Tracer™ Information Blog. This will be added to Accessibility Resources Subject Tracer™.