How does the Lean Startup Methodology ensure the viability of a business idea during early development?

The Lean Startup Methodology keeps a business idea viable by testing it quickly and cheaply with real customers, so you learn what works before spending too much money. First, you build a minimal product that shows the core value, then you ask customers for feedback and measure their reactions. If the data shows people want the product and are willing to pay, you iterate; if not, you pivot or stop. For example, a startup might create a simple landing page to gauge interest in a new app, and if visitors sign up, it builds the app further; if not, it changes the idea. This cycle of building, measuring, and learning reduces risk and ensures the idea meets real needs.