What exactly does the enable-background attribute do?
SvgSvg Problem Overview
What exactly does the enable-background attribute do?
I read the specification but still I don't understand it.
Svg Solutions
Solution 1 - Svg
It's supposed to make the background image available to child elements of the element it's specified on for things like filter effects that blend content with the background. There may be other uses, but that's the one I know.
If you don't have it set, then technically the element can't use backgrounds created by ancestors.
The only major browser that supported it (ever) was IE10/11, so it doesn't get used very much. (It's also there as boilerplate in every Illustrator SVG export - for no good reason.)
(It's also been deprecated by all the major browsers since 2014)
Solution 2 - Svg
As noted by Robert Longson in comments, attribute enable-background is deprecated at least since 2014.
> SVG 1.1 introduced the enable-background property. The property defined the back drop under the filter region at the time that the <filter> element was invoked. The concept defined by this property was identified to be incompatible with the model of stacking context in CSS at the time writing this specification. UAs can choose to implement the enable-background property as defined in SVG 1.1 but will not be compatible to this specification or to CSS Compositing and Blending [W3C Working Draft].
Solution 3 - Svg
> Deprecated: This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.