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. However, 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.

Requirements: JavaScript Enabled
Demo: http://lab.maltewassermann.com/viewport-resizer/
License: License Free