Why the size field matters most here
Every other converter on this site has an obvious output size: the input's. SVG does not. It is a set of drawing instructions, not a grid of pixels, so to convert SVG to PNG you have to choose a resolution, and that choice is the whole substance of the operation.
Leave the size fields empty and this tool uses whatever the file declares. That is frequently a 24 by 24 icon, because icon libraries export at their design size, and a 24 pixel PNG is rarely what anyone wanted. Set a width instead and the vector is rendered fresh at that resolution, with edges as crisp as the format allows. Unlike every raster tool here, upscaling an SVG is not only allowed but is the normal case, because there is no original pixel grid to degrade.
The viewBox problem other converters trip on
A lot of SVG files declare only a viewBox and no width or height. Figma and
Illustrator both export this way, and it is valid: the file says what coordinate
space it occupies without asserting a physical size.
Browsers report naturalWidth of zero for such a file. A converter that trusts
that number produces nothing, or a blank image, which is why so many online SVG
converters fail on exactly the files people most often need to convert. This tool
parses the viewBox and applies it as an explicit size before rendering, so those
files behave like any other.
Fonts and external references
Two things do not survive rasterization reliably, and both are worth checking before you convert a logo.
Fonts referenced by name need to be installed on the machine doing the render. When they are missing the browser silently substitutes something else, and your carefully kerned wordmark comes out in a default sans-serif. Converting text to outlines in your editor before export removes the risk entirely.
External images and stylesheets loaded by URL are blocked. The SVG is rendered from a local blob URL for privacy reasons, and that context cannot fetch remote resources. Self-contained files, which is nearly all of them, are unaffected.
What you get, and what you lose
You get a file that works everywhere: PNG opens in every editor, every CMS and every chat app, and needs no renderer.
You lose scalability. The PNG is fixed at the resolution you chose, so a version for a retina banner and a version for a favicon are two separate conversions. Keep the SVG as the master and rasterize whenever you need a specific size.