Reconciliation is a core concept in React that deals with efficiently updating the UI when there are changes in a component’s state or props. At its essence, reconciliation is the process React employs to determine which parts of the actual DOM need to be updated, without having to redraw the entire page.

Whenever there’s a change in the state or props of a component, React creates a new virtual DOM tree that represents the updated state of the UI. This new tree is then compared with the previous virtual DOM, a process known as “diffing”. By detecting the differences or “diffs” between the old and new trees, React can identify the minimal number of actual DOM updates required to reflect these changes.

Reconciliation ensures that only those components that truly need to be updated undergo the render phase, enhancing performance. The underlying principle React adheres to during this process is the idea that updating the real DOM is inherently costly. Minimizing direct DOM manipulations significantly boosts application performance and ensures a smoother user experience.

However, it’s crucial to understand that while reconciliation optimizes the number of DOM updates, it doesn’t guarantee the least number of updates. For this reason, React might sometimes update components that haven’t had changes in props or state. Yet, even with this consideration, the reconciliation process ensures that the UI remains consistent and updates are executed in a performant manner.

Reconciliation in React is an intelligent diffing mechanism, ensuring efficient and timely updates to the UI by minimizing unnecessary DOM changes. By understanding this process, developers can better appreciate the performance benefits React brings and how it maintains a consistent and up-to-date UI.

Previously at
Flag Argentina
time icon
Seasoned Software Engineer specializing in React.js development. Over 5 years of experience crafting dynamic web solutions and collaborating with cross-functional teams.