While working on responsive websites, we quickly want to see how the layout reacts to different screen sizes.

Viewport Resizer is a very useful bookmarklet for responsive-layout-testing with few clicks.

Once clicked, it shows a list of popular screen sizes and we can see the websites in those sizes by simply pressing them.

Viewport Resizer

Its page allows us to create a customized bookmarklet that includes the sizes we want.

The orientations of various sizes are already set but there is also an option to manually change the orientation.

There is support for media queries and it is touch-friendly.

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