Default background color of SVG root element

I'd like to set a default background color for the entire SVG document, to red for example.

<svg viewBox="0 0 500 600" style="background: red">/* content */</svg>

The solution above works but the background property of the style attribute is unfortunately not a standard one : http://www.w3.org/TR/SVG/styling.html#SVGStylingProperties, and so it gets removed during the cleaning process with SVG Cleaner.

Is there another way to declare this background color?

SVG 1.2 Tiny has viewport-fill I'm not sure how widely implemented this property is though as most browsers are targetting SVG 1.1 at this time. Opera implements it FWIW.

A more cross-browser solution currently would be to stick a <rect> element with width and height of 100% and fill="red" as the first child of the <svg> element, for example:

<rect width="100%" height="100%" fill="red"/>

Found this works in Safari. SVG only colors in with background-color where an element's bounding box covers. So, give it a border (stroke) with a zero pixel boundary. It fills in the whole thing for you with your background-color.

<svg style='stroke-width: 0px; background-color: blue;'> </svg>