Lowdefy is a config-first web stack that turns YAML files into production web applications, complete with forms, tables, charts, authentication, and live connections to your databases and APIs. You declare pages as trees of blocks (inputs, buttons, tables, charts, markdown), wire events to actions, and the runtime renders a responsive app without a frontend codebase to maintain. More than 50 logic operators handle conditions, lookups, formatting, and state, so dynamic behavior comes from config rather than custom JavaScript scattered across components. Requests run on the server against MongoDB, PostgreSQL, MySQL, REST APIs, Google Sheets, S3, Elasticsearch, and Stripe, keeping credentials off the browser entirely. Sign-in arrives through Auth.js with more than 75 providers, public and private pages, and role-based access control deciding who sees each page and block. When the built-in catalog runs out, npm plugins add custom blocks, connections, operators, actions, and auth providers, declared in the same YAML. Schema validation checks every property before the app serves traffic, and one framework upgrade improves every app built on it. Build once and run the server anywhere Node.js runs, from a single VPS to a container platform. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Apache-2.0 licensed.