React's reconciliation engine — understand how Fiber enables concurrent rendering, prioritization, and Suspense.
Five passes over the same idea, each from a different angle. Do them in order, or jump to whichever you need.
Fiber is React's internal reconciliation algorithm that replaced the old stack reconciler. It enables incremental rendering, allowing React to pause, abort, and resume work. Each fiber node represents a unit of work in the virtual DOM tree. Fiber powers concurrent features like transitions, Suspense, and streaming SSR.
