Quick Tip to Resize Windows in Firefox

It is essential to test websites at different screen resolutions to make sure that your visitors will be able to see the same contents even if they run a different resolution than the website was designed for. The quickest way to change the resolution of the Firefox window is a Javascript one liner.

Paste the following code into the address bar of Firefox and hit enter afterwards: javascript:window.resizeTo(800,600). This will change the resolution of the Firefox window to 800×600. Just change the values to different ones, for example (1024,800) if you want to use the Firefox browser in that resolution.

It is also possible to save this code as a new bookmark instead of pasting that code into the address bar. Right-click on the bookmarks toolbar and select New Bookmark from the menu. Put the code into the location field and enter a name that describes it

I have created bookmarks this way for the following screen resolutions and moved all of them in a folder called Check in the bookmarks toolbar: 640×480, 800×600, 1024×768 and 1280×1024