In programming, Gatsby is a free and open-source framework based on React that helps developers build fast, modern websites and applications. It utilizes React.js library, GraphQL, and a variety of other technologies to generate static HTML pages during the build process, resulting in a highly performant website. Additionally, it also offers features such as PWA (Progressive Web App) support, offline capabilities, image optimization, and other performance-enhancing features. Gatsby is also popular for its plugins and developer-friendly ecosystem, making it a popular choice for building high-performance and user-friendly web applications. Gatsby has built up 56,000 GitHub stars, with weekly npm downloads for the core package settling around 300,000 as the framework has matured.