In development mode, the code is automatically transpiled by Babel and hot-loaded to the browser by react-hot-loader plugin utilizing Webpack's HMR feature. With HMR, the changes made to the source files are reflected automatically on the browser without page reload. Page reload resets application state whereas hot reload preserves the state and only updates the changed part of the application. For further information on HMR, see Webpack’s HMR & React-Hot-Loader — The Missing Manual. Both server, web, mobile source code are written in Babel, and sharing some common frameworks.