> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/eslint/eslint/llms.txt
> Use this file to discover all available pages before exploring further.
# Universal Build
> Browser-compatible ESLint Linter for client-side linting
## Overview
The `eslint/universal` export provides a browser-compatible version of the ESLint Linter. This build is designed for client-side JavaScript environments where Node.js-specific features are not available.
## Import Path
```javascript theme={null}
import { Linter } from "eslint/universal";
```
Or using CommonJS:
```javascript theme={null}
const { Linter } = require("eslint/universal");
```
## What's Included
The universal build exports only the **Linter** class, which is the core linting engine without file system or configuration file dependencies.
Core linting engine that works in browser environments
## Differences from Node.js Build
The universal build differs from the main ESLint package:
| Feature | Main Package | Universal Build |
| ------------------- | ------------ | --------------- |
| ESLint class | ✅ Yes | ❌ No |
| Linter class | ✅ Yes | ✅ Yes |
| File system access | ✅ Yes | ❌ No |
| Config file loading | ✅ Yes | ❌ No |
| RuleTester | ✅ Yes | ❌ No |
| SourceCode | ✅ Yes | ❌ No |
| Browser compatible | ❌ No | ✅ Yes |
## Usage Example
```javascript theme={null}
import { Linter } from "eslint/universal";
const linter = new Linter();
// Define configuration inline
const config = {
rules: {
semi: "error",
quotes: ["error", "double"]
}
};
// Lint some code
const code = "const x = 'single quotes'";
const messages = linter.verify(code, config);
console.log(messages);
// [
// {
// ruleId: 'quotes',
// severity: 2,
// message: "Strings must use doublequote.",
// line: 1,
// column: 11
// }
// ]
```
## Browser Integration
Use a bundler (webpack, rollup, esbuild) to include `eslint/universal` in your browser bundle:
```javascript theme={null}
import { Linter } from "eslint/universal";
```
Instantiate the Linter in your browser code:
```javascript theme={null}
const linter = new Linter();
```
Define rules inline (no config file loading):
```javascript theme={null}
const config = {
languageOptions: {
ecmaVersion: 2022,
sourceType: "module"
},
rules: {
"no-unused-vars": "warn",
"no-console": "error"
}
};
```
Pass code strings directly to the linter:
```javascript theme={null}
const results = linter.verify(userCode, config);
displayResults(results);
```
## Online Code Editor Example
```html theme={null}
ESLint in Browser
```
## Use Cases
The universal build is ideal for:
* **Online code editors** (like CodeSandbox, StackBlitz)
* **Browser-based IDEs**
* **Educational platforms** teaching JavaScript
* **Static site generators** with client-side linting
* **Progressive web apps** with code editing features
## Limitations
The universal build cannot:
* Load configuration files from the file system
* Read `.eslintignore` files
* Auto-discover plugins
* Access the file system
* Use the ESLint class or RuleTester
## API Documentation
For detailed Linter API documentation, see:
Complete Linter class reference with all methods and options
## Bundle Size Considerations
The universal build is optimized for browser use but still includes all core ESLint functionality:
* **Core linting engine**: AST parsing, rule execution, message generation
* **Built-in rules**: All 294+ ESLint rules are included
* **Traversal and scope analysis**: Full AST traversal and scope management
Consider using tree-shaking and dynamic imports to reduce bundle size if you only need specific rules.
## Related
Full Linter API reference
Understand how ESLint works
Configure linting rules
Create custom rules