The error UnhandledSchemeError: Reading from "node:util" is not handled by plugins occurs because a Node.js module (like node:util) is being imported in an environment where it isn't properly handled, typically in a frontend context using Webpack, Vite, or similar tools.
Here’s how to fix it:
---
1. Identify the Problem
This error occurs because tools like Webpack or Vite cannot handle Node.js-specific modules (e.g., node:util) in a browser environment.
The node: prefix is a Node.js convention to explicitly import core modules, introduced in Node.js 16+.
Likely causes include:
Using a package designed for Node.js in a browser environment.
A misconfigured bundler (e.g., Webpack, Vite).
An outdated dependency trying to import node: modules.
---
2. Solutions
A. Check for Node.js Dependencies
If you’re using a library that is meant for Node.js (server-side), but you’re trying to use it in a browser environment, you need to either:
1. Use a browser-compatible version of the library.
2. Replace it with an equivalent library that works in the browser.
For example:
Replace util with browser-friendly alternatives like util-polyfill or similar.
---
B. Handle the node: Prefix in Webpack
If you’re using Webpack, ensure the resolve.fallback option is set correctly to handle Node.js core modules in a browser-like environment:
1. Install Polyfills: Install node-polyfill-webpack-plugin or specific polyfills for Node.js modules:
2. Update Webpack Config: Modify webpack.config.js to include the polyfill:
3. Alternative Fallbacks: If you don’t want to use node-polyfill-webpack-plugin, you can manually add specific fallbacks:
---
C. Fix Vite Configuration
For Vite, you can configure the vite.config.js file to handle Node.js modules:
1. Install Polyfills:
2. Update Vite Config: Add the polyfill to your vite.config.js:
---
D. Update Dependencies
Sometimes the issue arises due to outdated dependencies. Update your packages to their latest versions:
Check your package.json for any dependencies that might be server-specific and confirm they are browser-compatible.
---
E. Replace the node: Prefix
If the node: prefix is unnecessary or causing issues, you can try removing it in your imports. For example:
This may work in environments where util is automatically handled.
---
F. Use externals for Node.js Modules (if not needed)
If the node:util module is not required in your build (e.g., it's used only in server code), mark it as an external dependency in your bundler config.
For Webpack:
For Vite:
---
3. Debugging Steps
Inspect Dependencies: Run npm ls or check your package-lock.json to identify which library depends on node:util.
Verify Environment: Ensure you are using the correct libraries for your target environment (Node.js vs. browser).
Use console.log: Log the module resolution paths to confirm the issue source.
---
Here’s how to fix it:
---
1. Identify the Problem
This error occurs because tools like Webpack or Vite cannot handle Node.js-specific modules (e.g., node:util) in a browser environment.
The node: prefix is a Node.js convention to explicitly import core modules, introduced in Node.js 16+.
Likely causes include:
Using a package designed for Node.js in a browser environment.
A misconfigured bundler (e.g., Webpack, Vite).
An outdated dependency trying to import node: modules.
---
2. Solutions
A. Check for Node.js Dependencies
If you’re using a library that is meant for Node.js (server-side), but you’re trying to use it in a browser environment, you need to either:
1. Use a browser-compatible version of the library.
2. Replace it with an equivalent library that works in the browser.
For example:
Replace util with browser-friendly alternatives like util-polyfill or similar.
---
B. Handle the node: Prefix in Webpack
If you’re using Webpack, ensure the resolve.fallback option is set correctly to handle Node.js core modules in a browser-like environment:
1. Install Polyfills: Install node-polyfill-webpack-plugin or specific polyfills for Node.js modules:
JavaScript:
npm install node-polyfill-webpack-plugin2. Update Webpack Config: Modify webpack.config.js to include the polyfill:
JavaScript:
const NodePolyfillPlugin = require('node-polyfill-webpack-plugin');
module.exports = {
resolve: {
fallback: {
util: require.resolve("util/"),
},
},
plugins: [
new NodePolyfillPlugin(),
],
};3. Alternative Fallbacks: If you don’t want to use node-polyfill-webpack-plugin, you can manually add specific fallbacks:
JavaScript:
module.exports = {
resolve: {
fallback: {
util: require.resolve("util/"),
fs: false, // Disable unsupported modules
},
},
};---
C. Fix Vite Configuration
For Vite, you can configure the vite.config.js file to handle Node.js modules:
1. Install Polyfills:
JavaScript:
npm install rollup-plugin-node-polyfills2. Update Vite Config: Add the polyfill to your vite.config.js:
JavaScript:
import { defineConfig } from 'vite';
import nodePolyfills from 'rollup-plugin-node-polyfills';
export default defineConfig({
plugins: [
nodePolyfills(),
],
resolve: {
alias: {
util: 'util/',
},
},
});---
D. Update Dependencies
Sometimes the issue arises due to outdated dependencies. Update your packages to their latest versions:
JavaScript:
npm updateCheck your package.json for any dependencies that might be server-specific and confirm they are browser-compatible.
---
E. Replace the node: Prefix
If the node: prefix is unnecessary or causing issues, you can try removing it in your imports. For example:
JavaScript:
// Original problematic import
import { someFunction } from 'node:util';
// Replace with:
import { someFunction } from 'util';This may work in environments where util is automatically handled.
---
F. Use externals for Node.js Modules (if not needed)
If the node:util module is not required in your build (e.g., it's used only in server code), mark it as an external dependency in your bundler config.
For Webpack:
JavaScript:
module.exports = {
externals: {
util: 'commonjs util',
},
};For Vite:
JavaScript:
export default defineConfig({
build: {
rollupOptions: {
external: ['util'],
},
},
});---
3. Debugging Steps
Inspect Dependencies: Run npm ls or check your package-lock.json to identify which library depends on node:util.
Verify Environment: Ensure you are using the correct libraries for your target environment (Node.js vs. browser).
Use console.log: Log the module resolution paths to confirm the issue source.
---