Rules for XML prolog, DTD, and xmlns and version attributes in SVG

rules-for-xml-prolog-dtd-and-xmlns-and-version-attributes-in-svg.md

From two articles on stackoverflow and an MDN article:

In external SVG files (which should be served as image/svg+xml):

Include the prolog:

<?xml version="1.0" encoding="utf-8"?>

Include a DTD:

<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">

The xmlns attribute of the <svg> root element is required and the version attribute is recommended; the xmlns:xlink attribute is required only if the document uses xlink:

<svg version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">

In internal SVG inlined in HTML5:

The prolog should not be included.

The DTD should not be included.

The version attribute is recommended, but is ignored by every user agent.

The xmlns, and xmlns:xlink attributes are not required.