How can I upgrade my application to React 19

Step 1: Update Dependencies

Run the following command in your project directory to install React 19 and ReactDOM:

bash
npm install react@19 react-dom@19

If you are using Yarn, the command would be:

bash
yarn add react@19 react-dom@19

Step 2: Review Deprecated Features

Check the release notes for React 19 to identify any deprecated features that may affect your application. Make necessary updates to your code to accommodate these changes.

Step 3: Run Tests

Execute your test suite to ensure that everything works correctly with the new version. This will help identify any issues early in the upgrade process.

Step 4: Monitor Performance

After upgrading, monitor your application's performance and address any potential regressions that may occur due to the upgrade.

Additional Considerations

- New JSX Transform: Ensure that the new JSX transform is enabled in your project. If not, you may see warnings about using an outdated transform. This is crucial for optimizing performance in React 19[2][3].

- Codemods: Utilize codemods provided by the React team to help automate changes in your codebase. You can run the following command to apply common migrations:

bash
npx codemod@latest react/19/migration-recipe

This will help you transition to the new APIs and patterns introduced in React 19[3][6].

Following these steps will help ensure a smooth upgrade to React 19 while taking advantage of its new features and improvements.