I’ve seen SVGs generated containing an xmlns:serif namespace, for example:
<svg width="180" height="50" version="1.1" xmlns="http://www.w3.org/2000/svg"
xmlns:xlink="http://www.w3.org/1999/xlink" xml:space="preserve" xmlns:serif="http://www.serif.com/"...
I’m seeing this attribute flagged as an unregistered/unknown namespace, when the others in the same SVG are not. Serif’s site says nothing about it, and searching hasn’t found anything relevant either.
What SVG features are in this namespace, is it necessary, and why would it be considered invalid (for example by the W3C HTML5 validator)?
>Solution :
It’s markup litter, presumably from the folks who control the http://www.serif.com/ domain that appears in the namespace URI.
Conforming SVG processors must propagate and ignore unknown XML components from foreign namespaces:
5.11. Foreign namespaces and private data
SVG allows inclusion of elements from foreign namespaces anywhere
within the SVG content. In general, the SVG user agent must include
the unknown foreign-namespaced elements in the DOM but will ignore and
exclude them for rendering purposes.[…]
Additionally, SVG allows inclusion of attributes from foreign
namespaces on any SVG element. The SVG user agent must include unknown
attributes in the DOM but should otherwise ignore unknown attributes.