What actually happens when you convert a PNG to SVG, and when it's worth doing.
A PNG is a grid of pixels — zoom in far enough and you'll see the individual colored squares. An SVG is a set of mathematical shapes and paths. Converting a PNG to SVG means tracing the shapes in the pixel image and describing them as vector paths instead, so the result can be scaled to any size — a business card or a billboard — without ever looking blurry or pixelated.
Resizing a PNG up just stretches its existing pixels, which is why enlarged raster images look soft or blocky. A vector file has no fixed resolution at all — a circle in an SVG is stored as "a circle with this radius," not as thousands of individual pixels, so it renders crisply no matter how large or small it's displayed. That's also why SVGs are the required format for laser engravers, vinyl cutters, and CNC routers, which need actual path data to follow, not a pixel grid.
Conversion works best on images with clear, distinct edges — logos, line art, simple illustrations, and high-contrast photos. It traces boundaries between light and dark (or between colors, in multi-color mode), so a subject with a clean silhouette against its background converts more cleanly than a busy photo with soft gradients and low contrast throughout.
It'll be a traced, vectorized interpretation of it — clean edges and solid shapes rather than a pixel-for-pixel copy. For logos and line art the result is usually very close to the original; for detailed photos it reads more like a stylized outline than a photograph.
Uploading and previewing the result is free. Downloading the SVG/DXF files costs $0.99 per image.