Which statement about hydration is true?

Which statement about hydration is true?

• A. Hydration reconciles server-rendered HTML with client-side code, attaching event listeners without re-rendering the entire UI.
• B. Hydration renders both server and client HTML separately.
• C. Hydration is a technique to hydrate CSS styles on the client.
• D. Hydration is used to prefetch data before rendering.

Answer: (A)

Hydration is the process of taking server-rendered markup and wiring it up with client-side behavior, so the page becomes interactive without rebuilding the UI. The server already sent HTML that represents the initial UI, and hydration binds the client’s event handlers and state to that existing DOM. Because the markup already matches what the UI should look like, there’s no need to re-render the entire interface—only the JavaScript logic is activated and synchronized. That’s why the statement about reconciling server-rendered HTML with client-side code and attaching event listeners without re-rendering the whole UI is the correct description. The other choices describe separate ideas—rendering separate HTML on the client, styling-related hydration, or prefetching data—that aren’t what hydration does.

Hydration is the process of taking server-rendered markup and wiring it up with client-side behavior, so the page becomes interactive without rebuilding the UI. The server already sent HTML that represents the initial UI, and hydration binds the client’s event handlers and state to that existing DOM. Because the markup already matches what the UI should look like, there’s no need to re-render the entire interface—only the JavaScript logic is activated and synchronized. That’s why the statement about reconciling server-rendered HTML with client-side code and attaching event listeners without re-rendering the whole UI is the correct description. The other choices describe separate ideas—rendering separate HTML on the client, styling-related hydration, or prefetching data—that aren’t what hydration does.