Hot Module Replacement

Hot reloading is like swapping parts on a car while it's still driving. You change a button color and save, and the page in the browser changes right away. Whatever you typed in the form and any open dialog are usually still there, so you don't have to click through everything again.

Strictly speaking, there are two kinds. Hot module replacement (HMR) swaps only the code that changed and keeps state. Live reload reloads the whole page, and state is lost. Changing a component's styles or content usually gets the first kind. Changing config files or environment variables usually needs a dev server restart to take effect.

Hot reloading sometimes stops working: you change the code and the page doesn't change. First refresh the browser by hand. If that doesn't help, restart the dev server. If it still doesn't work, have the AI help you track it down.