max-len

Very long lines of code in any language can be difficult to read. In order to aid in readability and maintainability many coders have developed a convention to limit lines of code to X number of characters (traditionally 80 characters).

var foo = { "bar": "This is a bar.", "baz": { "qux": "This is a qux" }, "difficult": "to read" }; // very long

Rule Details

This rule enforces a maximum line length to increase code readability and maintainability. The length of a line is defined as the number of Unicode characters in the line.

Options

This rule can have up to two numbers as positional arguments (for code and tabWidth options), followed by an object option (provided positional arguments have priority):

• "code" (default 80) enforces a maximum line length
• "tabWidth" (default 4) specifies the character width for tab characters
• "comments" enforces a maximum line length for comments; defaults to value of code
• "ignorePattern" ignores lines matching a pattern; can only match a single line, needs to be double escaped when written in YAML or JSON and must be a string that can be passed to the RegExp constructor.
• "ignoreComments": true ignores all trailing comments and comments on their own line
• "ignoreTrailingComments": true ignores only trailing comments
• "ignoreUrls": true ignores lines that contain a URL
• "ignoreStrings": true ignores lines that contain a double-quoted or single-quoted string
• "ignoreTemplateLiterals": true ignores lines that contain a template literal
• "ignoreRegExpLiterals": true ignores lines that contain a RegExp literal

code

Examples of incorrect code for this rule with the default { "code": 80 } option:

/* eslint @stylistic/max-len: ["error", { "code": 80 }] */

var foo = { "bar": "This is a bar.", "baz": { "qux": "This is a qux" }, "difficult": "to read" };

incorrect

Examples of correct code for this rule with the default { "code": 80 } option:

/* eslint @stylistic/max-len: ["error", { "code": 80 }] */

var foo = {
  "bar": "This is a bar.",
  "baz": { "qux": "This is a qux" },
  "easier": "to read"
};

correct

tabWidth

Examples of incorrect code for this rule with the default { "tabWidth": 4 } option:

/* eslint @stylistic/max-len: ["error", { "code": 80, "tabWidth": 4 }] */

		var foo = { "bar": "This is a bar.", "baz": { "qux": "This is a qux" } };

incorrect

Examples of correct code for this rule with the default { "tabWidth": 4 } option:

/* eslint @stylistic/max-len: ["error", { "code": 80, "tabWidth": 4 }] */

		var foo = {
				"bar": "This is a bar.",
				"baz": { "qux": "This is a qux" }
		};

correct

comments

Examples of incorrect code for this rule with the { "comments": 65 } option:

/* eslint @stylistic/max-len: ["error", { "comments": 65 }] */

/**
 * This is a comment that violates the maximum line length we have specified
**/

incorrect

ignoreComments

Examples of correct code for this rule with the { "ignoreComments": true } option:

/* eslint @stylistic/max-len: ["error", { "ignoreComments": true }] */

/**
 * This is a really really really really really really really really really long comment
 **/

correct

ignoreTrailingComments

Examples of correct code for this rule with the { "ignoreTrailingComments": true } option:

/* eslint @stylistic/max-len: ["error", { "ignoreTrailingComments": true }] */

var foo = 'bar'; // This is a really really really really really really really long comment

correct

ignoreUrls

Examples of correct code for this rule with the { "ignoreUrls": true } option:

/* eslint @stylistic/max-len: ["error", { "ignoreUrls": true }] */

var url = 'https://www.example.com/really/really/really/really/really/really/really/long';

correct

ignoreStrings

Examples of correct code for this rule with the { "ignoreStrings": true } option:

/* eslint @stylistic/max-len: ["error", { "ignoreStrings": true }] */

var longString = 'this is a really really really really really really really long string!';

correct

ignoreTemplateLiterals

Examples of correct code for this rule with the { "ignoreTemplateLiterals": true } option:

/* eslint @stylistic/max-len: ["error", { "ignoreTemplateLiterals": true }] */

var longTemplateLiteral = `this is a really really really really really long template literal!`;

correct

ignoreRegExpLiterals

Examples of correct code for this rule with the { "ignoreRegExpLiterals": true } option:

/* eslint @stylistic/max-len: ["error", { "ignoreRegExpLiterals": true }] */

var longRegExpLiteral = /this is a really really really really really long regular expression!/;

correct

ignorePattern

NOTE

This option must be a string that can be passed to the RegExp constructor.

Examples of correct code for this rule with the ignorePattern option:

/* eslint @stylistic/max-len: [
  "error",
  { "ignorePattern": "^\\s*var\\s.+=\\s*require\\s*\\(" }
] */

var dep = require('really/really/really/really/really/really/really/really/long/module');

correct

Autofix limitations

max-len reports lines that exceed the configured limit, but it does not wrap them automatically. Some autofixable layout rules can remove line breaks or increase indentation. As a result, running eslint --fix may leave or introduce max-len violations.

ESLint does not coordinate a rule's fixes with the configured limit of max-len. Therefore, the output of --fix is not guaranteed to satisfy this rule.

Ways to avoid this

• Use a dedicated formatter such as Prettier, dprint, or oxfmt for layout, and disable overlapping autofixable layout rules. Formatters generally treat line width as a wrapping preference rather than a hard limit, so you may still need to relax or disable max-len.
• If you keep ESLint layout fixers enabled, choose compatible rule options and a suitable max-len limit, then manually resolve any remaining violations.
• Use options such as ignoreComments, ignoreStrings, ignoreUrls, or ignorePattern when specific kinds of long lines are acceptable.

Related Rules

• complexity
• max-depth
• max-nested-callbacks
• max-params
• max-statements