HTML check: Attribute “xmlns:sodipodi” not allowed here.

About This HTML Issue

The xmlns:sodipodi attribute declares the namespace for editor data that Inkscape inherited from Sodipodi, and HTML doesn't allow prefixed namespace declarations on <svg> or any other element.

Sodipodi was a vector drawing program written mainly by Lauris Kaplinski, and SVG was its native file format. In 2003 a group of its developers forked it to start Inkscape. Sodipodi itself stopped at version 0.34, released in February 2004. Inkscape kept the sodipodi: prefix for the features it inherited, so files saved by current versions still declare xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd" on the root <svg>. The URI is only a name for the namespace. Nothing downloads that DTD.

The prefix marks editor state. <sodipodi:namedview>, a child of the root <svg>, keeps the document's view settings: page and border colors, the grid, zoom and window position, the current layer, and any guide lines as <sodipodi:guide> children. On the root element, sodipodi:docname records the file name the drawing was last saved under.

Shapes and text carry their own sodipodi: attributes. sodipodi:nodetypes on a path has one letter per node (c for cusp, s for smooth, z for symmetric, a for auto-smooth), which the node tool reads to decide how a node's handles move. sodipodi:type marks a path drawn with a shape tool, such as star, arc or spiral, and attributes like sodipodi:sides and sodipodi:r1 keep the shape's parameters so Inkscape can bring its handles back. Lines of text get sodipodi:role="line" on their <tspan>. Browsers ignore all of it, and a star is drawn from the path's d attribute like any other path.

The HTML parser doesn't link prefixes to declarations. To it, xmlns:sodipodi is one attribute with a colon in its name and sodipodi:docname is another, and nothing connects the two. Delete only the declaration and every other sodipodi: name still fails on its own. The invalid example below gets 13 errors, and only one of them is about xmlns:sodipodi. The other 12 come from the sodipodi: attributes, such as Attribute "sodipodi:type" not allowed on element "path" at this point., and from <sodipodi:namedview> and <sodipodi:guide>, which the validator reports as completely-unknown elements in SVG content.

Delete xmlns:sodipodi, the <sodipodi:namedview> element with everything inside it, and every attribute that starts with sodipodi:. The image looks the same afterwards. Only Inkscape notices: the guides, grid and page settings are gone, and stars and spirals reopen as plain paths. Keep the original file for editing and put a cleaned copy in the page.

The same Inkscape file usually declares xmlns:inkscape, xmlns:rdf, xmlns:cc and xmlns:dc too, and each gets its own message. SVGO's removeEditorsNSData plugin, part of its default preset, removes the Sodipodi declaration and every sodipodi: element and attribute, and does the same for those four namespaces. If the whole file was pasted in, its <?xml version="1.0"?> line comes along too, and the validator reports it as an XML processing instruction.

Invalid example

<svg xmlns="http://www.w3.org/2000/svg"
  xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
  sodipodi:docname="star.svg"
  width="24" height="24" viewBox="0 0 24 24">
  <sodipodi:namedview pagecolor="#ffffff" showgrid="false">
    <sodipodi:guide position="12,12" orientation="1,0" />
  </sodipodi:namedview>
  <path sodipodi:type="star" sodipodi:sides="5"
    sodipodi:cx="12" sodipodi:cy="12" sodipodi:r1="10" sodipodi:r2="4"
    sodipodi:arg1="-1.5708" sodipodi:arg2="-0.9425"
    d="M12,2 14.35,8.76 21.51,8.91 15.8,13.24 17.88,20.09 12,16 6.12,20.09 8.2,13.24 2.49,8.91 9.65,8.76Z"
    fill="currentColor" />
</svg>

Valid example

<svg xmlns="http://www.w3.org/2000/svg"
  width="24" height="24" viewBox="0 0 24 24">
  <path d="M12,2 14.35,8.76 21.51,8.91 15.8,13.24 17.88,20.09 12,16 6.12,20.09 8.2,13.24 2.49,8.91 9.65,8.76Z"
    fill="currentColor" />
</svg>