Cannot Change SVG <use> icon size when linked to <symbol> - css

Question

I'm trying to use an SVG symbol in my mark-up, but I can't get the CSS to increase the size of the symbol being rendered inside a element?
I have a twitter logo defined in a set of tags, and then I'm referencing this with an xlink:href inside use tags. The icon is showing, but when I add CSS to the #box1 div holding the element the symbol isn't increasing or decreasing in size and seems to only rendering at the viewBox size.
Also, the SVG element itself when I hover it with the dev tools is rendering at 300 x 150px - but there is nothing on in the code with these measurements.
I'm really confused — any help would be awesome.
#box1 {
height: 10rem;
width: 10rem;
}
<defs style="display: none;">
<svg id="twitter" viewBox="0 0 19.19 15.95">
<symbol id="twitter-symbol"><title>twitter</title>
<path id="twitter-path" d="M19.19,1.92a8.76,8.76,0,0,1-2.28.64A3.9,3.9,0,0,0,18.63.32a6.87,6.87,0,0,1-2.52,1A3.87,3.87,0,0,0,13.23,0,4,4,0,0,0,9.32,4,3.41,3.41,0,0,0,9.44,5,11,11,0,0,1,1.32.72a4.29,4.29,0,0,0-.52,2A4,4,0,0,0,2.56,6.12,3.61,3.61,0,0,1,.76,5.6v0a4,4,0,0,0,3.16,4,4.35,4.35,0,0,1-1,.16,4.9,4.9,0,0,1-.76-.08,4,4,0,0,0,3.68,2.8A7.79,7.79,0,0,1,.92,14.19a6.78,6.78,0,0,1-.92,0A10.83,10.83,0,0,0,6,16c7.24,0,11.19-6.16,11.19-11.47V4a6.83,6.83,0,0,0,2-2" fill="#000">
</path>
</symbol>
</svg>
</defs>
<div id="box1">
<svg>
<use xlink:href="#twitter-symbol"/>
</svg>
</div>

Answer 1

The <defs>is an svg element. It always goes inside the svg. I've made a few changes and now it works. Please run the code and take a look at what I've done.
#box1 {
height: 10rem;
width: 10rem;
}
#twitter{display:none;}
<svg id="twitter">
<defs>
<symbol id="twitter-symbol"><title>twitter</title>
<path id="twitter-path" d="M19.19,1.92a8.76,8.76,0,0,1-2.28.64A3.9,3.9,0,0,0,18.63.32a6.87,6.87,0,0,1-2.52,1A3.87,3.87,0,0,0,13.23,0,4,4,0,0,0,9.32,4,3.41,3.41,0,0,0,9.44,5,11,11,0,0,1,1.32.72a4.29,4.29,0,0,0-.52,2A4,4,0,0,0,2.56,6.12,3.61,3.61,0,0,1,.76,5.6v0a4,4,0,0,0,3.16,4,4.35,4.35,0,0,1-1,.16,4.9,4.9,0,0,1-.76-.08,4,4,0,0,0,3.68,2.8A7.79,7.79,0,0,1,.92,14.19a6.78,6.78,0,0,1-.92,0A10.83,10.83,0,0,0,6,16c7.24,0,11.19-6.16,11.19-11.47V4a6.83,6.83,0,0,0,2-2" fill="#000">
</path>
</symbol>
</defs>
</svg>
<div id="box1">
<svg viewBox="0 0 19.19 15.95" width="24">
<use xlink:href="#twitter-symbol"/>
</svg>
</div>
I hope it helps.

Answer 2

You're using inline SVG code within your HTML, so I believe that SVG path needs a viewbox defined within it. For example, if you add viewBox="0 0 60 55" within your HTML SVG tag, you'll notice that the size will start to adjust. So edit this part of your HTML
<svg viewBox="0 0 60 55">
<use xlink:href="#twitter-symbol"/>
</svg>
To expand on your note where you found the size listed as 300x150, this is the default standard size that applies to HTML inline SVG code (per HTML5 specs). This differs sometimes depending on the browser.
Keep in mind, there a are a few different methods you can use when handling SVGs. Check out the guide below where they give a nice run down on SVG and how to manipulate it's size. You might find an alternative way that you would prefer to use.
https://css-tricks.com/scale-svg/