This document outlines the principles of the lean startup methodology. It discusses how startups differ from large corporations in their focus on developing hypotheses to test through customer development and iterative experimentation, rather than relying on business plans. The customer development model of customer discovery, validation, creation and company building is presented as a framework for searching for a scalable business model through continuous experimentation and pivoting. Key aspects of lean startups discussed include the business model canvas for visualizing hypotheses about the business, metrics like AARRR for validating learning, and case studies of companies like Zappos that exemplify the lean startup approach.