What attributes are not necessary in inline-SVG code - html

Question

I am working on a project that generates super strong passwords (for practise).
When using inline SVG, I was just wondering if there are any unnecessary attributes to the SVG code, because I'm trying to make it as short as possible.
In this specific snippet, I have a copy-to-clipboard icon.
Here is the code:
<?xml version="1.0" encoding="iso-8859-1"?>
<!-- Generator: Adobe Illustrator 19.1.0, SVG Export Plug-In . SVG Version: 6.00 Build 0) -->
<svg version="1.1" id="Capa_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
viewBox="0 0 488.3 488.3" style="enable-background:new 0 0 488.3 488.3;" xml:space="preserve">
<g>
<g>
<path d="M314.25,85.4h-227c-21.3,0-38.6,17.3-38.6,38.6v325.7c0,21.3,17.3,38.6,38.6,38.6h227c21.3,0,38.6-17.3,38.6-38.6V124
C352.75,102.7,335.45,85.4,314.25,85.4z M325.75,449.6c0,6.4-5.2,11.6-11.6,11.6h-227c-6.4,0-11.6-5.2-11.6-11.6V124
c0-6.4,5.2-11.6,11.6-11.6h227c6.4,0,11.6,5.2,11.6,11.6V449.6z"/>
<path d="M401.05,0h-227c-21.3,0-38.6,17.3-38.6,38.6c0,7.5,6,13.5,13.5,13.5s13.5-6,13.5-13.5c0-6.4,5.2-11.6,11.6-11.6h227
c6.4,0,11.6,5.2,11.6,11.6v325.7c0,6.4-5.2,11.6-11.6,11.6c-7.5,0-13.5,6-13.5,13.5s6,13.5,13.5,13.5c21.3,0,38.6-17.3,38.6-38.6
V38.6C439.65,17.3,422.35,0,401.05,0z"/>
</g>
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</svg>

Answer 1

Let's start with what is generally superfluous:
version="1.1" is not interpreted by any browser or renderer I know of.
style="enable-background:new 0 0 488.3 488.3;" While setting a style attribute in general might be good idea, the property enable-background is deprecated and was never implemented anywhere
The following might or might not have their place, depending on circumstances:
<?xml version="1.0" encoding="iso-8859-1"?> must be the first line of a XML-conforming standalone SVG. Note the encoding is not the default utf-8. If the SVG is used inline in HTML, browsers just ignore the line (if it is not the first line of the document), but strictly speaking its use in any other place breaks XML-wellformedness.
xmlns:xlink="http://www.w3.org/1999/xlink" Defining a namespace is only needed if you really have an element/attribute somewhere that uses it, for example a <use xlink:href="..." />. Even then, most browsers nowadays support the namespace-less href.
xml:space="preserve" is only usefull if you have <text> elements with <tspan> children. It will then govern whether whitespace between those child tags is interpreted as a space character.
x="0px" y="0px" On an outermost <svg> element in a standalone file, x and y are always ignored. If the SVG is embedded inline in other content, values other than the default 0 might have an effect, depending on the host language. (In HTML, you'll probably have to use CSS top and left instead.)
And finally, what is missing:
width and height have a default of 150px and 100px when the SVG is used inline. (For standalone files, the viewBox values will be used when they are missing.)
preserveAspectRatio has a default of xMidYMid meet. It defines how the viewBox is fitted into the SVGs dimensions if the aspect ratio of width, height and viewBox do not match.