Answer
Scheduler decides when work should run using priorities and interruption. Reconciler decides what to render by diffing and producing the fiber tree. Both combine to enable concurrency.
Quick Answer
The Scheduler determines when to run work — it uses the browser's message channel to schedule tasks between frames, preventing long tasks that block the main thread. The Reconciler determines what work to do — walking the fiber tree, comparing current and work-in-progress trees, and determining what DOM changes are needed.
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SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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Source: SugharaIQ