Describe an app in one plain sentence — "a URL shortener with rate limiting and click analytics" — and Blueprint designs the real architecture (services, gateways, databases, queues, third-party APIs) and draws it as a clean, tiered system diagram. Export it as PNG, SVG, or Mermaid, or edit the JSON and redraw. It's the difference between asking a chatbot and getting an actual, reusable diagram: the AI fills a strict schema, and a deterministic engine does the layout, the icons, and the polish.

Free, and runs right in your browser. No sign-up, no watermark-removal upsell, no catch. The free tier covers 40 diagrams a day.