SVG Optimizer runs svgo — the standard, widely-used SVG optimizer — entirely inside your browser via its dedicated browser build, so no file is ever sent to a server. Your SVG's markup is parsed, run through a configurable pipeline of cleanup plugins (removing comments, metadata, and redundant structure, and rounding numeric precision), and serialized back into minified XML, all inside a background worker.

Three presets cover the common cases without requiring any SVG internals knowledge: Safe sticks to svgo's standard, low-risk cleanup; Balanced adds multi-pass optimization and strips fixed width/height in favor of viewBox, which is usually the right choice for icons and illustrations embedded responsively; Aggressive pushes numeric rounding further for the smallest possible file. Power users can go further still, individually toggling any of the underlying cleanup plugins in the "Advanced" panel — useful when, say, an SVG's element IDs are referenced by external CSS and need to survive optimization unchanged.

Because a size number alone doesn't prove nothing broke, every optimization shows a side-by-side before/after render on a transparency checkerboard, alongside the exact byte size saved — so you can confirm the result looks right before downloading it.

Most of an unoptimized SVG's file size isn't the actual shape data — it's editor metadata (Illustrator or Figma export comments, unused <defs> entries, XML namespaces nothing references), verbose numeric precision (coordinates exported to far more decimal places than are ever visually distinguishable), and redundant attributes that could be inherited or simplified. A typical icon exported straight from a design tool can often shrink by 50–70% with zero visible difference, purely by removing content that was never rendering anything in the first place — which is why the Safe preset alone is usually worth running on every SVG before it ships, even without reaching for the more aggressive presets.