Substack Inc. operates a newsletter publishing platform that enables writers to build, monetize, and grow direct subscriber audiences through paid subscriptions and free content distribution. Founded in 2017 and headquartered in San Francisco, the company has established itself as a leading player in the creator economy by providing writers with tools to bypass traditional media gatekeepers and capture subscription revenue directly from readers. The platform achieved unicorn status with a $1.1 billion valuation, reflecting strong investor confidence in the subscription-based creator monetization model. Substack continues expanding its ecosystem with enhanced discovery features, community tools, and multimedia content capabilities to strengthen writer-subscriber relationships.