Glossary

Hydration is the process by which client-side JavaScript takes over markup that was pre-rendered or server-rendered, attaching event handlers and application state so that the page becomes interactive. Rather than generating the view from scratch in the browser, as with a pure client render, the framework reuses the existing DOM.

Hydration lets users see content quickly, before JavaScript has loaded, while still allowing rich interactivity afterwards. Because hydrating a whole page can be costly, techniques such as partial hydration, progressive hydration and "islands" hydrate only the interactive parts of a page.