StackScholar

React

Hydration

Attaching React to server-rendered HTML, reusing the markup rather than recreating it.

Why interviewers ask about it

Mismatches come from non-determinism in render: Date.now(), Math.random(), localStorage. Move those into useEffect so the first client render matches the server.

Related terms

SSR

Rendering components to HTML on the server so meaningful markup arrives in the first response.

Referential equality

Comparing by object identity rather than contents - what React.memo and dependency arrays use.

This term is part of the free Python Full-Stack interview preparation module - browse the full glossary for every definition.