Skip to content

Rendering

Hydration

The process of attaching JavaScript event listeners to server-rendered HTML in the browser.

Definition

After server-rendered HTML arrives in the browser, the JavaScript framework "hydrates" it — running again on the client to attach event handlers and reactive state. Hydration mismatches (server HTML differs from client render) cause warnings and can change canonical tags or page metadata after first paint, which crawlers may or may not see.

See also

Need this concept applied to your stack?

Glossary entries are intentionally short. Real engineering tradeoffs need a scoping call — bring the domain, the stack, and the question.