> ## 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.

# Rules Reference

> Complete guide to ESLint rules

# ESLint Rules

ESLint rules are the core of the linter - they analyze your code and report problems. Each rule is independent and can be configured individually.

## Rule Types

Rules are categorized by their purpose:

* **Problem Rules**: These rules identify code that will cause errors or unexpected behavior
* **Suggestion Rules**: These rules suggest alternate ways of doing things
* **Layout Rules**: These rules care about how the code looks rather than how it executes

## Using Rules

Configure rules in your ESLint configuration file:

```js theme={null}
module.exports = {
  rules: {
    'semi': ['error', 'always'],
    'quotes': ['error', 'single'],
    'no-unused-vars': 'warn'
  }
};
```

## Rule Severity

Each rule can be set to one of three severity levels:

* `"off"` or `0` - turn the rule off
* `"warn"` or `1` - turn the rule on as a warning (doesn't affect exit code)
* `"error"` or `2` - turn the rule on as an error (exit code will be 1)

## Browse Rules by Category

View rules organized by their purpose:

* [Problem Rules](/rules/categories#problem-rules) - Prevent errors and bugs
* [Suggestion Rules](/rules/categories#suggestion-rules) - Code improvements
* [Layout Rules](/rules/categories#layout-rules) - Code formatting

## Search Rules

Use the search below to find specific rules:

<Note>
  You can search by rule name, category, or keywords related to what the rule checks.
</Note>

## Popular Rules

### Problem Detection

* [array-callback-return](/rules/array-callback-return) - Enforce return statements in array callbacks
* [no-await-in-loop](/rules/no-await-in-loop) - Disallow await inside loops
* [no-constant-binary-expression](/rules/no-constant-binary-expression) - Disallow expressions that always evaluate to the same value

### Best Practices

* [eqeqeq](/rules/eqeqeq) - Require === and !==
* [no-eval](/rules/no-eval) - Disallow eval()
* [curly](/rules/curly) - Enforce consistent brace style

### Code Style

* [semi](/rules/semi) - Enforce semicolons
* [quotes](/rules/quotes) - Enforce quote style
* [indent](/rules/indent) - Enforce consistent indentation