Default background color of SVG root element

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>

It is the answer of @Robert Longson, now with code (there was originally no code, it was added later):

This answer uses:

https://stackoverflow.com/a/11293812/6747994

https://developer.mozilla.org/en-US/docs/Web/SVG/Tutorial/Fills_and_Strokes

Let me report a very simple solution I found, that is not written in previous answers. I also wanted to set background in an SVG, but I also want that this works in a standalone SVG file.

Well, this solution is really simple, in fact SVG supports style tags, so you can do something like

<svg xmlns="http://www.w3.org/2000/svg" width="50" height="50">
  <style>svg { background-color: red; }</style>
  <text>hello</text>
</svg>

I'm currently working on a file like this:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<?xml-stylesheet type="text/css" href="style.css" ?>
<svg
  xmlns="http://www.w3.org/2000/svg"
  version="1.1"
  width="100%"
  height="100%"
  viewBox="0 0 600 600">
...

And I tried to put this into style.css:

svg {
  background: #bf1f1f;
}

It's working on Chromium and Firefox, but I don't think that it's a good practice. EyeOfGnome image viewer doesn't render it, and Inkscape uses a special namespace to store such a background:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<svg
    xmlns="http://www.w3.org/2000/svg"
    xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
    version="1.1"
    ...
  <sodipodi:namedview
     pagecolor="#480000" ... >

Well, it seems that SVG root element is not part of paintable elements in SVG recommandations.

So I'd suggest to use the "rect" solution provided by Robert Longson because I guess that it is not a simple "hack". It seems to be the standard way to set a background with SVG.

Another workaround might be to use <div> of the same size to wrap the <svg>. After that, you will be able to apply "background-color", and "background-image" that will affect thesvg.

<div class="background">
  <svg></svg>
</div>

<style type="text/css">
.background{
  background-color: black; 
  /*background-image: */
}
</style>

background and background-color are not widely supported

the shortest code without is to draw a circle with a radius of 10000, this does also work for width-height-aspect-ratios different to viewBox.

<circle r="1e5" fill="red"/>