✅ What is Reconciliation in React?

Reconciliation in React is the internal process React uses to efficiently update the user interface when a component’s state or props change. Instead of re-rendering the entire UI from scratch, React creates a new Virtual DOM and compares it with the previous Virtual DOM using a technique called diffing. Based on this comparison, React updates only the specific parts of the real DOM that have actually changed. This selective update mechanism is what makes React applications fast, smooth, and highly performance-optimized, even when working with complex and dynamic user interfaces.

⚙️ How Reconciliation Works

The reconciliation process happens in three main steps. First is the render phase, where React re-renders the component whenever state or props change and generates a new Virtual DOM tree. Next comes the diffing algorithm, where React compares the new Virtual DOM with the old one. If elements are of the same type, React keeps the existing DOM node and updates only the changed attributes. If elements are of different types, React removes the old node and creates a new one. When working with lists, React relies on keys to identify which items were added, updated, or removed. Finally, in the commit phase, React applies only the required changes to the real DOM, avoiding unnecessary re-renders and improving overall performance.

✅ Example of Reconciliation

Consider a simple counter component where clicking a button updates a number displayed on the screen. When the button is clicked, React does not re-render the entire component tree. Instead, it detects that only the text showing the count has changed and updates just that specific part of the DOM. The button and its surrounding container remain untouched. This targeted update is a direct result of the reconciliation process.

🌟 Key Points to Remember

Reconciliation helps React applications stay fast by updating only the necessary DOM nodes. The diffing algorithm enables efficient comparison between old and new Virtual DOM trees. Using proper keys in lists is essential, as it allows React to correctly identify elements and avoid unnecessary re-renders.

Reconciliation in React Explained with Example (2025 Guide)