> ## 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.

# Quick Start Guide

> Get up and running with ESLint in under 5 minutes. This guide walks you through installation, configuration, and your first lint.

# Quick Start Guide

Get ESLint analyzing your JavaScript code in under 5 minutes. This guide will walk you through the essentials.

## Prerequisites

Before you begin, ensure you have Node.js installed:

<Note>
  **Required**: Node.js `^20.19.0`, `^22.13.0`, or `>=24` built with SSL support.

  Check your version: `node --version`
</Note>

## Installation & Setup

<Steps>
  <Step title="Initialize ESLint Configuration">
    Run the interactive configuration wizard to set up ESLint for your project:

    ```bash theme={null}
    npm init @eslint/config@latest
    ```

    This command will:

    * Detect your project type (JavaScript, TypeScript, React, etc.)
    * Ask about your code style preferences
    * Install required dependencies
    * Create an `eslint.config.js` file

    <Tip>
      The wizard is smart enough to detect if you're using React, Vue, or TypeScript and will configure ESLint accordingly.
    </Tip>
  </Step>

  <Step title="Run Your First Lint">
    Lint a single file:

    ```bash theme={null}
    npx eslint yourfile.js
    ```

    Or lint an entire directory:

    ```bash theme={null}
    npx eslint src/
    ```

    <CodeGroup>
      ```bash Success (no issues) theme={null}
      $ npx eslint src/index.js
      # No output means no problems found!
      ```

      ```bash With Errors theme={null}
      $ npx eslint src/index.js

      /path/to/src/index.js
        1:1   error  'x' is assigned a value but never used  no-unused-vars
        3:10  error  'foo' is not defined                     no-undef

      ✖ 2 problems (2 errors, 0 warnings)
      ```
    </CodeGroup>
  </Step>

  <Step title="Fix Problems Automatically">
    Many ESLint errors can be fixed automatically. Run with the `--fix` flag:

    ```bash theme={null}
    npx eslint --fix yourfile.js
    ```

    This will automatically fix:

    * Spacing and indentation issues
    * Missing semicolons
    * Quote style inconsistencies
    * And many other stylistic problems

    <Warning>
      The `--fix` flag modifies your files in place. Make sure your code is committed or backed up before running it.
    </Warning>
  </Step>

  <Step title="Add Lint Script to package.json">
    Add ESLint to your npm scripts for easy access:

    ```json package.json theme={null}
    {
      "scripts": {
        "lint": "eslint .",
        "lint:fix": "eslint --fix ."
      }
    }
    ```

    Now you can run:

    ```bash theme={null}
    npm run lint      # Check for problems
    npm run lint:fix  # Fix problems automatically
    ```
  </Step>
</Steps>

## Understanding the Config File

The configuration wizard creates an `eslint.config.js` file. Here's what a basic config looks like:

```js eslint.config.js theme={null}
import { defineConfig } from "eslint/config";

export default defineConfig([
  {
    files: ["**/*.js", "**/*.cjs", "**/*.mjs"],
    rules: {
      "prefer-const": "warn",
      "no-constant-binary-expression": "error",
    },
  },
]);
```

### Configuration Breakdown

<AccordionGroup>
  <Accordion title="files" icon="file">
    Specifies which files ESLint should analyze. Supports glob patterns:

    ```js theme={null}
    files: ["**/*.js", "**/*.cjs", "**/*.mjs"]
    ```

    This matches all `.js`, `.cjs`, and `.mjs` files in any directory.
  </Accordion>

  <Accordion title="rules" icon="list-check">
    Configures individual rules with severity levels:

    * `"off"` or `0` - Disable the rule
    * `"warn"` or `1` - Show warning (exit code 0)
    * `"error"` or `2` - Show error (exit code 1)

    ```js theme={null}
    rules: {
      "no-unused-vars": "error",
      "no-console": "warn",
      "quotes": ["error", "double"],
    }
    ```
  </Accordion>

  <Accordion title="extends" icon="layer-group">
    Import configurations from presets:

    ```js theme={null}
    import js from "@eslint/js";

    export default defineConfig([
      js.configs.recommended,  // Use recommended rules
      {
        // Your custom rules
      },
    ]);
    ```
  </Accordion>
</AccordionGroup>

## Common Rules to Start With

Here are some essential rules from the ESLint source code:

<CardGroup cols={2}>
  <Card title="no-unused-vars" icon="exclamation-triangle">
    **Type**: Problem\
    **Recommended**: ✓

    Disallow unused variables to keep your code clean.

    ```js theme={null}
    // ❌ Error
    const x = 5; // 'x' is never used

    // ✓ Correct
    const x = 5;
    console.log(x);
    ```
  </Card>

  <Card title="no-undef" icon="question-circle">
    **Type**: Problem\
    **Recommended**: ✓

    Disallow undefined variables to catch typos early.

    ```js theme={null}
    // ❌ Error
    console.log(foo); // 'foo' is not defined

    // ✓ Correct
    const foo = 'bar';
    console.log(foo);
    ```
  </Card>

  <Card title="prefer-const" icon="lock">
    **Type**: Suggestion\
    **Fixable**: ✓

    Suggest using const for variables that are never reassigned.

    ```js theme={null}
    // ⚠ Warning
    let x = 5; // 'x' is never reassigned

    // ✓ Correct
    const x = 5;
    ```
  </Card>

  <Card title="no-debugger" icon="bug">
    **Type**: Problem\
    **Recommended**: ✓

    Disallow debugger statements in production code.

    ```js theme={null}
    // ❌ Error
    debugger;

    // ✓ Use proper debugging tools instead
    ```
  </Card>
</CardGroup>

## CLI Options Quick Reference

Here are the most commonly used CLI options from ESLint's source:

```bash theme={null}
# Fix problems automatically
eslint --fix file.js

# Use a specific config file
eslint -c custom-config.js file.js

# Specify output format
eslint --format json file.js

# Set maximum warnings before error
eslint --max-warnings 10 .

# Lint with quiet mode (errors only)
eslint --quiet file.js

# Debug mode for troubleshooting
eslint --debug file.js
```

<Tip>
  For a complete list of CLI options, run `npx eslint --help` or check the [options.js](https://github.com/eslint/eslint/blob/main/lib/options.js) source file.
</Tip>

## What's Next?

<CardGroup cols={2}>
  <Card title="Deep Dive into Installation" icon="download" href="/installation">
    Learn about advanced installation options, pnpm setup, and TypeScript configuration
  </Card>

  <Card title="Configuration Guide" icon="gear" href="https://eslint.org/docs/latest/use/configure">
    Master ESLint's powerful configuration system
  </Card>

  <Card title="Rules Reference" icon="book" href="https://eslint.org/docs/rules/">
    Browse all 200+ built-in rules with examples
  </Card>

  <Card title="Create Custom Rules" icon="code" href="https://eslint.org/docs/latest/extend/custom-rules">
    Build your own rules to enforce project-specific patterns
  </Card>
</CardGroup>

## Troubleshooting

<AccordionGroup>
  <Accordion title="ESLint is not finding my config file">
    Make sure your config file is named `eslint.config.js`, `eslint.config.mjs`, or `eslint.config.cjs` and is in your project root.

    You can also specify a config file explicitly:

    ```bash theme={null}
    npx eslint -c path/to/config.js file.js
    ```
  </Accordion>

  <Accordion title="Getting 'Parsing error' messages">
    This usually means ESLint can't parse your JavaScript syntax. If you're using modern syntax or TypeScript:

    ```bash theme={null}
    npm install --save-dev @typescript-eslint/parser
    ```

    Then update your config:

    ```js theme={null}
    import tsParser from "@typescript-eslint/parser";

    export default defineConfig([
      {
        languageOptions: {
          parser: tsParser,
        },
      },
    ]);
    ```
  </Accordion>

  <Accordion title="Rules are not being applied">
    Check that:

    1. The `files` pattern matches your source files
    2. The rule is spelled correctly (e.g., `no-unused-vars`, not `no-unused-variables`)
    3. Your config file is being loaded (run with `--debug` flag)

    ```bash theme={null}
    npx eslint --debug file.js
    ```
  </Accordion>
</AccordionGroup>

## Need Help?

* Join the [Discord community](https://eslint.org/chat)
* Ask questions on [GitHub Discussions](https://github.com/eslint/eslint/discussions)
* Check the [FAQ](https://eslint.org/docs/latest/use/faq)