React minified error #123 occurs when the internal reconciliation transaction class or batching strategy is not properly injected into React's update system, typically indicating a setup or initialization issue.
This error occurs in React's minified production build when the internal reconciliation transaction class or batching strategy has not been properly configured. React uses an internal transaction system to batch updates and manage how the reconciler processes changes to the DOM. When error #123 appears, it means this core system is misconfigured or incompletely initialized, preventing React from properly handling state updates, prop changes, and DOM reconciliation. This is fundamentally a configuration problem rather than a logic error in your component code—it indicates that React itself hasn't been properly set up to run.
In development, React provides detailed error messages instead of minified codes. This will show you exactly what initialization step failed.
# If using Create React App
npm start # Uses development build by default
# If using custom setup, ensure NODE_ENV is not set to production
NODE_ENV=development npm startThe development build will reveal the actual problem causing error #123.
Check that React and ReactDOM are properly installed and match compatible versions.
npm list react react-dom
# Should show something like:
# [email protected]
# [email protected]
# If versions don't match or are missing, reinstall
rm package-lock.json node_modules
npm installEnsure both react and react-dom are present in package.json dependencies.
Delete the build output directory and rebuild from scratch to ensure the production build is created correctly.
# For Create React App
npm run build
# For custom setup (example)
rm -rf dist/
npm run build
# For Webpack
rm -rf dist/
webpack --mode productionA clean rebuild often resolves issues caused by incomplete or corrupted build artifacts.
If using a custom webpack or build configuration, verify that React's initialization code is not being stripped or mangled.
// webpack.config.js - example
module.exports = {
mode: 'production',
entry: './src/index.js',
output: {
filename: 'bundle.js',
path: __dirname + '/dist',
},
// Ensure no aggressive tree-shaking or mangling of React internals
optimization: {
usedExports: true,
// Avoid over-aggressive minification
minimize: true,
},
};Refer to your bundler's documentation for proper React handling.
Update to the latest stable version of React and ReactDOM to ensure all fixes and initialization code are included.
npm update react react-dom
# Or specify a specific version
npm install react@latest react-dom@latestIf you're on an old version, update to a newer stable release. Check [React's release notes](https://react.dev) for any known initialization issues.
Ensure your application entry point (typically src/index.js or src/main.js) properly imports and initializes React and ReactDOM.
// src/index.js
import React from 'react';
import ReactDOM from 'react-dom/client';
import App from './App';
const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(
<React.StrictMode>
<App />
</React.StrictMode>
);Missing or incorrect initialization will prevent React's internal systems from setting up properly.
Error #123 is a rare but serious sign of a broken React setup. It's not a bug in your component code—it's a configuration or build process issue. The minified production build intentionally strips full error messages to reduce bundle size, so switching to the development build is essential for debugging. In older versions of React (pre-16), this error could occur with certain custom setups or when using middleware that wasn't fully compatible. Modern React versions are more robust, so upgrading often resolves this issue. If you're building a custom JavaScript bundler or modifying React's core initialization, ensure you're not accidentally breaking the transaction/batching system that React depends on.
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