Does a re-render always update the DOM?
Quick answer
No. Re-render means React re-runs the component function; reconciliation then commits only the actual differences to the real DOM.
In detail
Rendering and committing are separate phases. A re-render produces a new virtual DOM tree; React diffs it against the previous tree and touches the real DOM only where something changed. So many re-renders result in zero DOM mutations and are cheap. This is why you should profile before optimising re-renders — most are harmless.
Why interviewers ask this: Corrects the common belief that every render is expensive.
This is 1 of 118+ questions in the React Interview Kit
Get every question with detailed answers, follow-ups and real code — plus coding challenges and a last-minute revision sheet. One-time payment, instant access.
⚡ Get the React Interview Kit → ₹399