React Compiler

React Compiler is a new compiler that we’ve open sourced to get feedback from the community. It is a build-time only tool that automatically optimizes your React app. It works with plain JavaScript, and understands the Rules of React, so you don’t need to rewrite any code to use it.

eslint-plugin-react-hooks also includes an ESLint rule that surfaces the analysis from the compiler right in your editor. We strongly recommend everyone use the linter today. The linter does not require that you have the compiler installed, so you can use it even if you are not ready to try out the compiler.

The compiler is currently released as rc, and is available to try out on React 17+ apps and libraries. To install the RC:

Or, if you’re using Yarn:

If you are not using React 19 yet, please see the section below for further instructions.

What does the compiler do?

In order to optimize applications, React Compiler automatically memoizes your code. You may be familiar today with memoization through APIs such as useMemo, useCallback, and React.memo. With these APIs you can tell React that certain parts of your application don’t need to recompute if their inputs haven’t changed, reducing work on updates. While powerful, it’s easy to forget to apply memoization or apply them incorrectly. This can lead to inefficient updates as React has to check parts of your UI that don’t have any meaningful changes.

The compiler uses its knowledge of JavaScript and React’s rules to automatically memoize values or groups of values within your components and hooks. If it detects breakages of the rules, it will automatically skip over just those components or hooks, and continue safely compiling other code.

If your codebase is already very well-memoized, you might not expect to see major performance improvements with the compiler. However, in practice memoizing the correct dependencies that cause performance issues is tricky to get right by hand.

function FriendList({ friends }) {
  const onlineCount = useFriendOnlineCount();
  if (friends.length === 0) {
    return <NoFriends />;
  }
  return (
    <div>
      <span>{onlineCount} online</span>
      {friends.map((friend) => (
        <FriendListCard key={friend.id} friend={friend} />
      ))}
      <MessageButton />
    </div>
  );
}

// **Not** memoized by React Compiler, since this is not a component or hook
function expensivelyProcessAReallyLargeArrayOfObjects() { /* ... */ }

// Memoized by React Compiler since this is a component
function TableContainer({ items }) {
  // This function call would be memoized:
  const data = expensivelyProcessAReallyLargeArrayOfObjects(items);
  // ...
}

Should I try out the compiler?

The compiler is now in RC and has been tested extensively in production. While it has been used in production at companies like Meta, rolling out the compiler to production for your app will depend on the health of your codebase and how well you’ve followed the Rules of React.

You don’t have to rush into using the compiler now. It’s okay to wait until it reaches a stable release before adopting it. However, we do appreciate trying it out in small experiments in your apps so that you can provide feedback to us to help make the compiler better.

Getting Started

In addition to these docs, we recommend checking the React Compiler Working Group for additional information and discussion about the compiler.

Installing eslint-plugin-react-hooks

React Compiler also powers an ESLint plugin. You can try it out by installing eslint-plugin-react-hooks@^6.0.0-rc.1.

See our editor setup guide for more details.

The ESLint plugin will display any violations of the rules of React in your editor. When it does this, it means that the compiler has skipped over optimizing that component or hook. This is perfectly okay, and the compiler can recover and continue optimizing other components in your codebase.

Rolling out the compiler to your codebase

Existing projects

The compiler is designed to compile functional components and hooks that follow the Rules of React. It can also handle code that breaks those rules by bailing out (skipping over) those components or hooks. However, due to the flexible nature of JavaScript, the compiler cannot catch every possible violation and may compile with false negatives: that is, the compiler may accidentally compile a component/hook that breaks the Rules of React which can lead to undefined behavior.

For this reason, to adopt the compiler successfully on existing projects, we recommend running it on a small directory in your product code first. You can do this by configuring the compiler to only run on a specific set of directories:

const ReactCompilerConfig = {
  sources: (filename) => {
    return filename.indexOf('src/path/to/dir') !== -1;
  },
};

When you have more confidence with rolling out the compiler, you can expand coverage to other directories as well and slowly roll it out to your whole app.

New projects

If you’re starting a new project, you can enable the compiler on your entire codebase, which is the default behavior.

Using React Compiler with React 17 or 18

React Compiler works best with React 19 RC. If you are unable to upgrade, you can install the extra react-compiler-runtime package which will allow the compiled code to run on versions prior to 19. However, note that the minimum supported version is 17.

You should also add the correct target to your compiler config, where target is the major version of React you are targeting:

// babel.config.js
const ReactCompilerConfig = {
  target: '18' // '17' | '18' | '19'
};

module.exports = function () {
  return {
    plugins: [
      ['babel-plugin-react-compiler', ReactCompilerConfig],
    ],
  };
};

Using the compiler on libraries

React Compiler can also be used to compile libraries. Because React Compiler needs to run on the original source code prior to any code transformations, it is not possible for an application’s build pipeline to compile the libraries they use. Hence, our recommendation is for library maintainers to independently compile and test their libraries with the compiler, and ship compiled code to npm.

Because your code is pre-compiled, users of your library will not need to have the compiler enabled in order to benefit from the automatic memoization applied to your library. If your library targets apps not yet on React 19, specify a minimum target and add react-compiler-runtime as a direct dependency. The runtime package will use the correct implementation of APIs depending on the application’s version, and polyfill the missing APIs if necessary.

Library code can often require more complex patterns and usage of escape hatches. For this reason, we recommend ensuring that you have sufficient testing in order to identify any issues that might arise from using the compiler on your library. If you identify any issues, you can always opt-out the specific components or hooks with the 'use no memo' directive.

Similarly to apps, it is not necessary to fully compile 100% of your components or hooks to see benefits in your library. A good starting point might be to identify the most performance sensitive parts of your library and ensuring that they don’t break the Rules of React, which you can use eslint-plugin-react-compiler to identify.

Usage

Babel

The compiler includes a Babel plugin which you can use in your build pipeline to run the compiler.

After installing, add it to your Babel config. Please note that it’s critical that the compiler run first in the pipeline:

// babel.config.js
const ReactCompilerConfig = { /* ... */ };

module.exports = function () {
  return {
    plugins: [
      ['babel-plugin-react-compiler', ReactCompilerConfig], // must run first!
      // ...
    ],
  };
};

babel-plugin-react-compiler should run first before other Babel plugins as the compiler requires the input source information for sound analysis.

Vite

If you use Vite, you can add the plugin to vite-plugin-react:

// vite.config.js
const ReactCompilerConfig = { /* ... */ };

export default defineConfig(() => {
  return {
    plugins: [
      react({
        babel: {
          plugins: [
            ["babel-plugin-react-compiler", ReactCompilerConfig],
          ],
        },
      }),
    ],
    // ...
  };
});

Next.js

Please refer to the Next.js docs for more information.

Remix

Install vite-plugin-babel, and add the compiler’s Babel plugin to it:

// vite.config.js
import babel from "vite-plugin-babel";

const ReactCompilerConfig = { /* ... */ };

export default defineConfig({
  plugins: [
    remix({ /* ... */}),
    babel({
      filter: /\.[jt]sx?$/,
      babelConfig: {
        presets: ["@babel/preset-typescript"], // if you use TypeScript
        plugins: [
          ["babel-plugin-react-compiler", ReactCompilerConfig],
        ],
      },
    }),
  ],
});

Webpack

A community webpack loader is