Non-standard: This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
The Window.sizeToContent() method sizes the window according to its content. In order for it to work, the DOM content should be loaded when this function is called—for example, once the DOMContentLoaded event has been thrown.
Since Firefox 20, the minimal size of the window is clamped to prevent the window from being too small for the user to interact with.
