Responsive designs adapt to different screen sizes to provide a presentation that is suitable for different kinds of devices, such as mobile phones or tablets. The Responsive Design View makes it easy to see how your website or web app will look on different screen sizes.

The screenshot below shows a page on the mobile version of Wikipedia viewed with a 320 by 480 content area.

The Responsive Design View is convenient because you can quickly and precisely change the size of the content area.

Of course, you could just resize the browser window: but making the browser window smaller makes all your other tabs smaller too, and can make the browser's interface much harder to use.

While the Responsive Design View is enabled, you can continue browsing as you normally would in the resized content area.

Enabling and disabling

There are three ways to enable Responsive Design View mode:

  • Select "Responsive Design View" from the Web Developer submenu in the Firefox Menu (or Tools menu if you display the menu bar or are on OS X)
  • Press the "Responsive Design View" button in the Toolbox's toolbar
  • Press Ctrl + Shift + M, (or Cmd + Opt + M on OS X)

and three ways to switch off Responsive Design View:

  • Select the "Responsive Design View" menu item again
  • Click the "close" button in the top-left corner of the window
  • Press Ctrl + Shift + M, (or Cmd + Opt + M on OS X). Prior to Firefox 34, Escape would also close Responsive Design View.

Resizing

You can resize the content area in one of two ways:

  • using the "Select size" control
  • clicking and dragging on the controls on the right and bottom sides of the content area, or in the bottom-right corner

If you resize using click-and-drag you can hold down the Control key (command on Max OS X) to slow down the speed at which the area resizes. This makes it easier to set the size precisely.

Responsive Design View controls

Along the top of the window in which Responsive Design View displays the page, there are five controls:

Close Close Responsive Design View and return to normal browsing.
Select size

Choose from a number of preset width x height combinations, or define your own.

From Firefox 33 onwards, the numbers displayed here are directly editable, so you can easily define custom dimensions.

Portrait/Landscape Switch the screen between portrait and landscape view.

Simulate touch events

Enable/disable touch event simulation: while touch event simulation is enabled, mouse events are translated into touch events.

Take screenshot

Take a screenshot of the content area.

Screenshots are saved to Firefox's default download location.