React Upgrade

What you'll learn

Understand the main ideas in React Upgrade.
See a working example and explanation to help you learn by doing.
Follow a clear path to the next lesson in this topic.

When to use this lesson

Use this lesson when you want to understand the key concepts behind React Upgrade.

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Upgrading React

React is a constantly evolving library. Upgrading your app gives you bug fixes, security updates, performance improvements, and access to newer APIs.

The safest upgrade path is usually a small one: update React, run the app, fix warnings, and test the pages that rely on forms, routing, and custom hooks.

How to Upgrade

To upgrade a React application to the latest version, you generally need to update the react and react-dom packages in your project's package.json file.

You can do this easily using npm in your terminal:

npm install react@latest react-dom@latest

After upgrading, you should always check the official React blog for any breaking changes and migration guides, especially when moving between major versions (e.g., from React 17 to React 18).

Upgrade Checklist

Update react and react-dom together.
Run your test suite and click through the main user flows.
Fix console warnings before shipping.
Verify third-party packages support the new version.

Common Issues After an Upgrade

Custom components may need a small refactor if APIs changed.
Legacy lifecycle methods or outdated dependencies may warn or fail.
Strict Mode can surface side effects that were previously hidden.

Best Practice

If you are managing a production app, upgrade on a branch, test carefully, and deploy in small steps. A stable upgrade is more valuable than rushing to the newest version.