React Key & Re-render Quiz
Keys, reconciliation, and why memo children still re-render — ten questions with instant feedback and a score you can share.
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About this tool
Keys look like a small detail until a sorted table keeps the wrong input values. This quiz covers the cases that show up in code review — index keys, fragments, memo props, and resetting state on purpose.
Answers encode in the URL so you can share a result or resume later. No data leaves your browser.
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