My advice, for web pages: always specify the <svg> width and height attributes, or the width and height properties in a style attribute, because if non-inline CSS doesn’t load (more common, for various reasons, than most people realise), the SVG will fill the available width. And you probably don’t want your 24×24 icon rendered at 1900×1900.

(For web apps, I feel I can soften a bit, as you’re more likely to be able to rely on styles. But I would still suggest having appropriate width/height attributes, even if you promptly override them by CSS.)

This, so much this. It is extremely annoying when I have a slow connection and I have to scroll down ages to get to the page content.