Configuration

It enables ALL rules for this group.

Enforce that the accessKey attribute is not used on any HTML element.

Enforce that elements that do not support ARIA roles, states, and properties do not have those attributes.

Enforce that autoFocus prop is not used on elements.

Disallow target="_blank" attribute without rel="noreferrer"

Enforces that no distracting elements are used.

The scope prop should be used only on elements.

Enforce that interactive ARIA roles are not assigned to non-interactive HTML elements.

Enforce that tabIndex is not assigned to non-interactive HTML elements.

Prevent the usage of positive integers on tabIndex property

Enforce img alt prop does not contain the word "image", "picture", or "photo".

Enforce explicit role property is not the same as implicit/default role property on an element.

Enforces the usage of the title element for the svg element.

It enables the recommended rules for this group

Enforce that all elements that require alternative text have meaningful information to relay back to the end user.

Enforce that anchors have content and that the content is accessible to screen readers.

Enforce that elements with ARIA roles must have all required ARIA attributes for that role.

Enforces the usage of the attribute type for the element button

Enforce that heading elements (h1, h2, etc.) have content and that the content is accessible to screen readers. Accessible means that it is not hidden using the aria-hidden prop.

Enforce that html element has lang attribute.

Enforces the usage of the attribute title for the element iframe.

Enforce onClick is accompanied by at least one of the following: onKeyUp, onKeyDown, onKeyPress.

Enforce onMouseOver / onMouseOut are accompanied by onFocus / onBlur.

Enforces that audio and video elements must have a track for captions.

Enforce that all anchors are valid, and they are navigable elements.

Ensures that ARIA properties aria-* are all valid.

Enforce that ARIA state and property values are valid.

Ensure that the attribute passed to the lang attribute is a correct ISO language and/or country.

It enables ALL rules for this group.

Disallow primitive type aliases and misleading types.

Disallow functions that exceed a given Cognitive Complexity score.

Disallow unnecessary boolean casts

Prefer for...of statement instead of Array.forEach.

Disallow unclear usage of consecutive space characters in regular expression literals

This rule reports when a class has no non-static members, such as for a class used exclusively as a static namespace.

Disallow unnecessary catch clauses.

Disallow unnecessary constructors.

Disallow empty exports that don't change anything in a module file.

Disallow unnecessary fragments

Disallow unnecessary labels.

Disallow renaming import, export, and destructured assignments to the same name.

Disallow useless case in switch statements.

Disallow useless this aliasing.

Disallow using any or unknown as type constraint.

Disallow the use of void operators, which is not a familiar operator.

Disallow with statements in non-strict contexts.

It enables the recommended rules for this group

Promotes the use of .flatMap() when map().flat() are used together.

Enforce the usage of a literal access to properties over computed property access.

Enforce using concise optional chain instead of chained logical expressions.

Disallow number literal object member names which are not base10 or uses underscore as separator

Discard redundant terms from logical expressions.

The maximum complexity score that we allow. Anything higher is considered excessive.

It enables ALL rules for this group.

Prevent passing of children as props.

Prevents from having const variables being re-assigned.

Disallow constant expressions in conditions

Disallow returning a value from a constructor.

Disallows empty destructuring patterns.

Disallow calling global object properties as functions

Disallow function and var declarations that are accessible outside their block.

Prevents the incorrect use of super() inside classes. It also checks whether a call super() is missing from classes that extends other constructors.

Disallow new operators with the Symbol object.

Disallow \8 and \9 escape sequences in string literals.

Disallow literal numbers that lose precision

Prevent the usage of the return value of React.render.

Disallow assignments where both sides are exactly the same.

Disallow returning a value from a setter

Disallow comparison of expressions modifying the string case with non-compliant value.

Disallow lexical declarations in switch clauses.

Prevents the usage of variables that haven't been declared inside the document.

Avoid using unnecessary continue.

Disallow unreachable code

Ensures the super() constructor is called exactly once on every code path in a class constructor before this is accessed if the class has a superclass

Disallow control flow statements in finally blocks.

Disallow the use of optional chaining in contexts where the undefined value is not allowed.

Disallow unused labels.

Disallow unused variables.

This rules prevents void elements (AKA self-closing elements) from having children.

Disallow returning a value from a function with the return type 'void'

It enables the recommended rules for this group

Enforce all dependencies are correctly specified in a React hook.

Enforce that all React hooks are being called from the Top Level component functions.

Require calls to isNaN() when checking for NaN.

Enforce "for" loop update clause moving the counter in the right direction.

Require generator functions to contain yield.

A list of Unix shell style patterns. Biome will ignore files/folders that will match these patterns.

Tells Biome to not emit diagnostics when handling files that doesn't know

A list of Unix shell style patterns. Biome will handle only those files/folders that will match these patterns.

The maximum allowed size for source code files in bytes. Files above this limit will be ignored for performance reasons. Defaults to 1 MiB

Stores whether formatting should be allowed to proceed if a given file has syntax errors

A list of Unix shell style patterns. The formatter will ignore files/folders that will match these patterns.

A list of Unix shell style patterns. The formatter will include files/folders that will match these patterns.

The size of the indentation, 2 by default (deprecated, use indent-width)

The indent style.

The size of the indentation, 2 by default

What's the max width of a line. Defaults to 80.

The name of the hook

The "position" of the closure function, starting from zero.

Example

The "position" of the array of dependencies, starting from zero.

List of safe hooks

Formatting options

A list of global bindings that should be ignored by the analyzers

If defined here, they should not emit diagnostics.

Parsing options

Whether to add non-necessary parentheses to arrow functions. Defaults to "always".

Control the formatter for JavaScript (and its super languages) files.

The size of the indentation applied to JavaScript (and its super languages) files. Default to 2.

The indent style applied to JavaScript (and its super languages) files.

The size of the indentation applied to JavaScript (and its super languages) files. Default to 2.

The type of quotes used in JSX. Defaults to double.

What's the max width of a line, applied to JavaScript (and its super languages) files. Defaults to 80.

When properties in objects are quoted. Defaults to asNeeded.

The type of quotes used in JavaScript code. Defaults to double.

Whether the formatter prints semicolons for all statements or only in for statements where it is necessary because of ASI.

Print trailing commas wherever possible in multi-line comma-separated syntactic structures. Defaults to "all".

It enables the experimental and unsafe parsing of parameter decorators

These decorators belong to an old proposal, and they are subject to change.

Formatting options

Parsing options

Control the formatter for JSON (and its super languages) files.

The size of the indentation applied to JSON (and its super languages) files. Default to 2.

The indent style applied to JSON (and its super languages) files.

The size of the indentation applied to JSON (and its super languages) files. Default to 2.

What's the max width of a line, applied to JSON (and its super languages) files. Defaults to 80.

Allow parsing comments in .json files

Allow parsing trailing commas in .json files

if false, it disables the feature and the linter won't be executed. true by default

A list of Unix shell style patterns. The formatter will ignore files/folders that will match these patterns.

A list of Unix shell style patterns. The formatter will include files/folders that will match these patterns.

List of rules

Allowed cases for TypeScript enum member names.

If false, then consecutive uppercase are allowed in camel and pascal cases. This does not affect other [Case].

It enables ALL rules for this group.

Usually, the definition in the standard library is more precise than what people come up with or the used constant exceeds the maximum precision of the number type.

Disallow two keys with the same name inside a JSON object.

Disallow empty block statements and static blocks.

Disallow empty character classes in regular expression literals.

Enforce that non-interactive ARIA roles are not assigned to interactive HTML elements.

Disallow new operators with global non-constructor functions.

Enforce proper usage of new and constructor.

Disallow shorthand assign when variable appears on both sides.

Disallow this and super in static contexts.

Disallow unused imports.

Disallow else block when the if block breaks early.

Disallow unnecessary nested block statements.

It enables the recommended rules for this group

Enforce that tabIndex is assigned to non-interactive HTML elements with aria-activedescendant.

Use arrow functions over function expressions.

Enforce the use of as const over literal type and type annotation.

Enforce the use of import type when an import only has specifiers with type qualifier.

Disallows package private imports.

Require assignment operator shorthand where possible.

Enables the organization of imports

A list of Unix shell style patterns. The formatter will ignore files/folders that will match these patterns.

A list of Unix shell style patterns. The formatter will include files/folders that will match these patterns.

Stores whether formatting should be allowed to proceed if a given file has syntax errors

The size of the indentation, 2 by default (deprecated, use indent-width)

The indent style.

The size of the indentation, 2 by default

What's the max width of a line. Defaults to 80.

if false, it disables the feature and the linter won't be executed. true by default

List of rules

if false, it disables the feature and the linter won't be executed. true by default

Specific configuration for the Json language

A list of Unix shell style patterns. The formatter will ignore files/folders that will match these patterns.

A list of Unix shell style patterns. The formatter will include files/folders that will match these patterns.

Specific configuration for the JavaScript language

Specific configuration for the Json language

Specific configuration for the Json language

Specific configuration for the Json language

It enables ALL rules for this group.

Disallow the use of spread (...) syntax on accumulators.

Disallow the use of the delete operator.

It enables the recommended rules for this group

A list of names that should trigger the rule

It enables ALL rules. The rules that belong to nursery won't be enabled.

It enables the lint rules recommended by Biome. true by default.

It enables ALL rules for this group.

Prevent the usage of dangerous JSX props

Report when a DOM element or a component uses both children and dangerouslySetInnerHTML prop.

It enables the recommended rules for this group

It enables ALL rules for this group.

Disallow the use of arguments

Disallow comma operator.

Disallow implicit true values on JSX boolean attributes

Disallow type annotations for variables, parameters, and class properties initialized with a literal expression.

Disallow the use of TypeScript's namespaces.

Disallow negation in the condition of an if statement if it has an else clause.

Disallow non-null assertions using the ! postfix operator.

Disallow reassigning function parameters.

Disallow the use of parameter properties in class constructors.

This rule allows you to specify global variable names that you don’t want to use in your application.

Disallow the use of constants which its value is the upper-case version of its name.

Disallow template literals if interpolation and special-character handling are not needed

Disallow the use of var

It enables the recommended rules for this group

Requires following curly brace conventions.

Enforce using else if instead of nested if in else clauses.

Require const declarations for variables that are never reassigned after declared.

Enforce default function parameters and optional function parameters to be last.

Require that each enum member value be explicitly initialized.

Disallow the use of Math.pow in favor of the ** operator.

This rule enforces the use of <>...</> over ....

Require all enum members to be literal values.

Enforce naming conventions for everything across a codebase.

Disallow parseInt() and Number.parseInt() in favor of binary, octal, and hexadecimal literals

Prevent extra closing tags for components without children

When expressing array types, this rule promotes the usage of T[] shorthand instead of Array.

Enforces switch clauses have a single statement, emits a quick fix wrapping the statements in a block.

Disallow multiple variable declarations in the same variable statement

Prefer template literals over string concatenation.

Enforce the use of while loops instead of for loops when the initializer and update expressions are not needed.

It enables ALL rules for this group.

Discourage the usage of Array index in keys.

Disallow assignments in expressions.

Disallows using an async function as a Promise executor.

Disallow reassigning exceptions in catch clauses.

Disallow reassigning class members.

Prevent comments from being inserted as text nodes

Disallow comparing against -0

Disallow labeled statements that are not loops.

Disallow void type outside of generic or return types.

Disallow the use of console.log

Disallow TypeScript const enum

Prevents from having control characters and some escape sequences that match control characters in regular expressions.

Disallow the use of debugger

Require the use of === and !==

Disallow duplicate case labels.

Disallow duplicate class members.

Prevents JSX properties to be assigned multiple times.

Prevents object literals having more than one property declaration for the same name.

Disallow duplicate function parameter name.

Disallow the declaration of empty interfaces.

Disallow the any type usage.

Prevents the wrong usage of the non-null assertion operator (!) in TypeScript files.

Disallow fallthrough of switch clauses.

Disallow reassigning function declarations.

Use Number.isFinite instead of global isFinite.

Use Number.isNaN instead of global isNaN.

Disallow assigning to imported bindings

Disallow labels that share a name with a variable

Disallow direct use of Object.prototype builtins.

Disallow variable, function, class, and type redeclarations in the same scope.

Prevents from having redundant "use strict".

Disallow comparisons where both sides are exactly the same.

Disallow identifiers from shadowing restricted names.

Disallow sparse arrays

Disallow unsafe declaration merging between interfaces and classes.

Disallow using unsafe negation.

It enables the recommended rules for this group

Enforce default clauses in switch statements to be last

Enforce get methods to always return a value.

Use Array.isArray() instead of instanceof Array.

Require using the namespace keyword over the module keyword to declare TypeScript namespaces.

This rule verifies the result of typeof $expr unary expressions is being compared to valid values, either string literals containing valid type names or other typeof expressions

The kind of client.

Whether Biome should integrate itself with the VCS client

The folder where Biome should check for VCS files. By default, Biome will use the same folder where biome.json was found.

If Biome can't find the configuration, it will attempt to use the current working directory. If no current working directory can't be found, Biome won't use the VCS integration, and a diagnostic will be emitted

Whether Biome should use the VCS ignore file. When [true], Biome will ignore the files specified in the ignore file.