Where the weight actually is
SVGs exported from Illustrator, Figma or Inkscape carry a surprising amount of baggage: generator comments, editor-specific namespaces, metadata blocks, and coordinates written to fifteen decimal places. None of it affects the rendering, and on icon-sized files it is routinely half the bytes.
Coordinate precision is usually the biggest single win. A path point specified to 0.000001 of a unit is describing a position far finer than any screen can render.
Why both versions are rendered
Any optimiser can make a file smaller by breaking it. The two panels show the original and the result drawn side by side, so you can see immediately whether anything shifted. That check matters most when you lower the decimal places — push it too far and curves visibly flatten.
Start with Keep as-is, which only strips genuine cruft and cannot change the picture. Reach for rounding only if you need more, and look at the comparison before you accept it.
What is deliberately left alone
IDs and classes are preserved, because CSS or JavaScript elsewhere on your page may target them, and a minifier cannot know. Gradient and filter references stay intact. Numbers inside URLs, class names and text content are never touched — only genuine geometry attributes are tidied.
<title> is removed by default since it is often just a filename, but tick the option to keep it when it carries a real accessible name for screen readers.
Frequently asked questions
Should I gzip as well?
Yes, and it compounds. SVG is text, so gzip or brotli on your server typically halves it again. Optimising first still helps — there is less to compress and the browser parses less.
Are my images uploaded?
No. The file is parsed and rewritten in the page; nothing is transmitted.
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