x="0".SVGs exported by design tools carry luggage the browser ignores: editor namespaces, layer metadata, comments from whoever drew it, and verbose attributes for values that are already the default. Stripping them rarely changes the rendered result but often changes the file size noticeably — useful when the SVG is inlined in a stylesheet or shipped in a bundle where every KB counts. Inline SVGs benefit twice: fewer bytes in the markup, and fewer nodes for the browser to walk when it lays out the page. The removal list tells you what actually went, so a file that barely shrank is diagnosable rather than mysterious.
The metadata toggle also removes title and desc elements — the accessible names screen readers announce for standalone SVGs. If your icon is a meaningful image rather than decoration, turn that toggle off and keep them. This is a text-level optimizer rather than a rendering engine, so give complex artwork a quick visual check afterwards; the copy-and-download loop is fast enough to make that trivial.
Also useful: Image Format Converter, CSS Minifier, and HTML Minifier.