Why this downloads a file instead of giving a URL#
Placeholder image services that generate an image on the fly from a URL pattern (like /800x600) require a server to stay online for as long as anything references that URL — a dependency that can silently break a project months later if the service shuts down or changes its API. This tool draws the image once, in the browser, and hands over a real downloadable file with no ongoing dependency on anything staying up.