web dev//rendering//hydration

JavaScript takes the HTML produced by SSR and adds interactive behavior to it. The server delivers a finished model; JavaScript then connects the buttons and the motors.

JavaScript takes the HTML produced by SSR and adds interactive behavior to it. The server delivers a finished model; JavaScript then connects the buttons and the motors.

SSR gives visible HTML, then hydration runs, then the same HTML is a live interactive application.

The page is readable before hydration and usable after it; the gap between the two is where "the button did nothing" bugs live. Frameworks fight it with partial hydration (only the interactive islands) and streaming.

Hydration is what makes SSR plus a rich SPA possible: server-rendered first paint, client-driven navigation afterwards.