# Rules Rules focus on *standard css* and aim to be valuable to the majority of users. In addition to these rules there are [plugins](/docs/user-guide/plugins.md), which are rules built by the community that support methodologies, toolsets, *non-standard* CSS features, or very specific use cases. Don't forget to look at the list of [plugins](/docs/user-guide/plugins.md) for more ways to lint. Every rule is standalone and turned off by default. None of the rules have default values for their options. ## List of rules Here are all the rules within stylelint, grouped by the [*thing*](http://apps.workflower.fi/vocabs/css/en) they apply to. ### Color - [`color-hex-case`](../../src/rules/color-hex-case/README.md): Specify lowercase or uppercase for hex colors. - [`color-hex-length`](../../src/rules/color-hex-length/README.md): Specify short or long notation for hex colors. - [`color-named`](../../src/rules/color-named/README.md): Require (where possible) or disallow named colors. - [`color-no-hex`](../../src/rules/color-no-hex/README.md): Disallow hex colors. - [`color-no-invalid-hex`](../../src/rules/color-no-invalid-hex/README.md): Disallow invalid hex colors. ### Font family - [`font-family-name-quotes`](../../src/rules/font-family-name-quotes/README.md): Specify whether or not quotation marks should be used around font family names. ### Font weight - [`font-weight-notation`](../../src/rules/font-weight-notation/README.md): Require numeric or named (where possible) `font-weight` values. ### Function - [`function-blacklist`](../../src/rules/function-blacklist/README.md): Specify a blacklist of disallowed functions. - [`function-calc-no-unspaced-operator`](../../src/rules/function-calc-no-unspaced-operator/README.md): Disallow an unspaced operator within `calc` functions. - [`function-comma-newline-after`](../../src/rules/function-comma-newline-after/README.md): Require a newline or disallow whitespace after the commas of functions. - [`function-comma-newline-before`](../../src/rules/function-comma-newline-before/README.md): Require a newline or disallow whitespace before the commas of functions. - [`function-comma-space-after`](../../src/rules/function-comma-space-after/README.md): Require a single space or disallow whitespace after the commas of functions. - [`function-comma-space-before`](../../src/rules/function-comma-space-before/README.md): Require a single space or disallow whitespace before the commas of functions. - [`function-linear-gradient-no-nonstandard-direction`](../../src/rules/function-linear-gradient-no-nonstandard-direction/README.md): Disallow direction values in `linear-gradient()` calls that are not valid according to the [standard syntax](https://developer.mozilla.org/en-US/docs/Web/CSS/linear-gradient#Syntax). - [`function-max-empty-lines`](../../src/rules/function-max-empty-lines/README.md): Limit the number of adjacent empty lines within functions. - [`function-name-case`](../../src/rules/function-name-case/README.md): Specify lowercase or uppercase for function names. - [`function-parentheses-newline-inside`](../../src/rules/function-parentheses-newline-inside/README.md): Require a newline or disallow whitespace on the inside of the parentheses of functions. - [`function-parentheses-space-inside`](../../src/rules/function-parentheses-space-inside/README.md): Require a single space or disallow whitespace on the inside of the parentheses of functions. - [`function-url-data-uris`](../../src/rules/function-url-data-uris/README.md): Require or disallow data URIs for urls. - [`function-url-no-scheme-relative`](../../src/rules/function-url-no-scheme-relative/README.md): Disallow scheme-relative urls. - [`function-url-quotes`](../../src/rules/function-url-quotes/README.md): Require or disallow quotes for urls. - [`function-url-scheme-whitelist`](../../src/rules/function-url-scheme-whitelist/README.md): Specify a whitelist of allowed url schemes. - [`function-whitelist`](../../src/rules/function-whitelist/README.md): Specify a whitelist of allowed functions. - [`function-whitespace-after`](../../src/rules/function-whitespace-after/README.md): Require or disallow whitespace after functions. ### Number - [`number-leading-zero`](../../src/rules/number-leading-zero/README.md): Require or disallow a leading zero for fractional numbers less than 1. - [`number-max-precision`](../../src/rules/number-max-precision/README.md): Limit the number of decimal places allowed in numbers. - [`number-no-trailing-zeros`](../../src/rules/number-no-trailing-zeros/README.md): Disallow trailing zeros in numbers. ### String - [`string-no-newline`](../../src/rules/string-no-newline/README.md): Disallow (unescaped) newlines in strings. - [`string-quotes`](../../src/rules/string-quotes/README.md): Specify single or double quotes around strings. ### Length - [`length-zero-no-unit`](../../src/rules/length-zero-no-unit/README.md): Disallow units for zero lengths. ### Time - [`time-no-imperceptible`](../../src/rules/time-no-imperceptible/README.md): Disallow `animation` and `transition` less than or equal to 100ms. ### Unit - [`unit-blacklist`](../../src/rules/unit-blacklist/README.md): Specify a blacklist of disallowed units. - [`unit-case`](../../src/rules/unit-case/README.md): Specify lowercase or uppercase for units. - [`unit-no-unknown`](../../src/rules/unit-no-unknown/README.md): Disallow unknown units. - [`unit-whitelist`](../../src/rules/unit-whitelist/README.md): Specify a whitelist of allowed units. ### Value - [`value-keyword-case`](../../src/rules/value-keyword-case/README.md): Specify lowercase or uppercase for keywords values. - [`value-no-vendor-prefix`](../../src/rules/value-no-vendor-prefix/README.md): Disallow vendor prefixes for values. ### Value list - [`value-list-comma-newline-after`](../../src/rules/value-list-comma-newline-after/README.md): Require a newline or disallow whitespace after the commas of value lists. - [`value-list-comma-newline-before`](../../src/rules/value-list-comma-newline-before/README.md): Require a newline or disallow whitespace before the commas of value lists. - [`value-list-comma-space-after`](../../src/rules/value-list-comma-space-after/README.md): Require a single space or disallow whitespace after the commas of value lists. - [`value-list-comma-space-before`](../../src/rules/value-list-comma-space-before/README.md): Require a single space or disallow whitespace before the commas of value lists. - [`value-list-max-empty-lines`](../../src/rules/value-list-max-empty-lines/README.md): Limit the number of adjacent empty lines within value lists. ### Custom property - [`custom-property-empty-line-before`](../../src/rules/custom-property-empty-line-before/README.md): Require or disallow an empty line before custom properties. - [`custom-property-no-outside-root`](../../src/rules/custom-property-no-outside-root/README.md): Disallow custom properties outside of `:root` rules. - [`custom-property-pattern`](../../src/rules/custom-property-pattern/README.md): Specify a pattern for custom properties. ### Shorthand property - [`shorthand-property-no-redundant-values`](../../src/rules/shorthand-property-no-redundant-values/README.md): Disallow redundant values in shorthand properties. ### Property - [`property-blacklist`](../../src/rules/property-blacklist/README.md): Specify a blacklist of disallowed properties. - [`property-case`](../../src/rules/property-case/README.md): Specify lowercase or uppercase for properties. - [`property-no-unknown`](../../src/rules/property-no-unknown/README.md): Disallow unknown properties. - [`property-no-vendor-prefix`](../../src/rules/property-no-vendor-prefix/README.md): Disallow vendor prefixes for properties. - [`property-whitelist`](../../src/rules/property-whitelist/README.md): Specify a whitelist of allowed properties. ### Keyframe declaration - [`keyframe-declaration-no-important`](../../src/rules/keyframe-declaration-no-important/README.md): Disallow `!important` within keyframe declarations. ### Declaration - [`declaration-bang-space-after`](../../src/rules/declaration-bang-space-after/README.md): Require a single space or disallow whitespace after the bang of declarations. - [`declaration-bang-space-before`](../../src/rules/declaration-bang-space-before/README.md): Require a single space or disallow whitespace before the bang of declarations. - [`declaration-colon-newline-after`](../../src/rules/declaration-colon-newline-after/README.md): Require a newline or disallow whitespace after the colon of declarations. - [`declaration-colon-space-after`](../../src/rules/declaration-colon-space-after/README.md): Require a single space or disallow whitespace after the colon of declarations. - [`declaration-colon-space-before`](../../src/rules/declaration-colon-space-before/README.md): Require a single space or disallow whitespace before the colon of declarations. - [`declaration-empty-line-before`](../../src/rules/declaration-empty-line-before/README.md): Require or disallow an empty line before declarations. - [`declaration-no-important`](../../src/rules/declaration-no-important/README.md): Disallow `!important` within declarations. - [`declaration-property-unit-blacklist`](../../src/rules/declaration-property-unit-blacklist/README.md): Specify a blacklist of disallowed property and unit pairs within declarations. - [`declaration-property-unit-whitelist`](../../src/rules/declaration-property-unit-whitelist/README.md): Specify a whitelist of allowed property and unit pairs within declarations. - [`declaration-property-value-blacklist`](../../src/rules/declaration-property-value-blacklist/README.md): Specify a blacklist of disallowed property and value pairs within declarations. - [`declaration-property-value-whitelist`](../../src/rules/declaration-property-value-whitelist/README.md): Specify a whitelist of allowed property and value pairs within declarations. ### Declaration block - [`declaration-block-no-duplicate-properties`](../../src/rules/declaration-block-no-duplicate-properties/README.md): Disallow duplicate properties within declaration blocks. - [`declaration-block-no-ignored-properties`](../../src/rules/declaration-block-no-ignored-properties/README.md): Disallow property values that are ignored due to another property value in the same rule. - [`declaration-block-no-redundant-longhand-properties`](../../src/rules/declaration-block-no-redundant-longhand-properties/README.md): Disallow longhand properties that can be combined into one shorthand property. - [`declaration-block-no-shorthand-property-overrides`](../../src/rules/declaration-block-no-shorthand-property-overrides/README.md): Disallow shorthand properties that override related longhand properties within declaration blocks. - [`declaration-block-properties-order`](../../src/rules/declaration-block-properties-order/README.md): Specify the order of properties within declaration blocks. - [`declaration-block-semicolon-newline-after`](../../src/rules/declaration-block-semicolon-newline-after/README.md): Require a newline or disallow whitespace after the semicolons of declaration blocks. - [`declaration-block-semicolon-newline-before`](../../src/rules/declaration-block-semicolon-newline-before/README.md): Require a newline or disallow whitespace before the semicolons of declaration blocks. - [`declaration-block-semicolon-space-after`](../../src/rules/declaration-block-semicolon-space-after/README.md): Require a single space or disallow whitespace after the semicolons of declaration blocks. - [`declaration-block-semicolon-space-before`](../../src/rules/declaration-block-semicolon-space-before/README.md): Require a single space or disallow whitespace before the semicolons of declaration blocks. - [`declaration-block-single-line-max-declarations`](../../src/rules/declaration-block-single-line-max-declarations/README.md): Limit the number of declaration within single line declaration blocks. - [`declaration-block-trailing-semicolon`](../../src/rules/declaration-block-trailing-semicolon/README.md): Require or disallow a trailing semicolon within declaration blocks. ### Block - [`block-closing-brace-empty-line-before`](../../src/rules/block-closing-brace-empty-line-before/README.md): Require or disallow an empty line before the closing brace of blocks. - [`block-closing-brace-newline-after`](../../src/rules/block-closing-brace-newline-after/README.md): Require a newline or disallow whitespace after the closing brace of blocks. - [`block-closing-brace-newline-before`](../../src/rules/block-closing-brace-newline-before/README.md): Require a newline or disallow whitespace before the closing brace of blocks. - [`block-closing-brace-space-after`](../../src/rules/block-closing-brace-space-after/README.md): Require a single space or disallow whitespace after the closing brace of blocks. - [`block-closing-brace-space-before`](../../src/rules/block-closing-brace-space-before/README.md): Require a single space or disallow whitespace before the closing brace of blocks. - [`block-no-empty`](../../src/rules/block-no-empty/README.md): Disallow empty blocks. - [`block-no-single-line`](../../src/rules/block-no-single-line/README.md): Disallow single-line blocks. - [`block-opening-brace-newline-after`](../../src/rules/block-opening-brace-newline-after/README.md): Require a newline after the opening brace of blocks. - [`block-opening-brace-newline-before`](../../src/rules/block-opening-brace-newline-before/README.md): Require a newline or disallow whitespace before the opening brace of blocks. - [`block-opening-brace-space-after`](../../src/rules/block-opening-brace-space-after/README.md): Require a single space or disallow whitespace after the opening brace of blocks. - [`block-opening-brace-space-before`](../../src/rules/block-opening-brace-space-before/README.md): Require a single space or disallow whitespace before the opening brace of blocks. ### Selector - [`selector-attribute-brackets-space-inside`](../../src/rules/selector-attribute-brackets-space-inside/README.md): Require a single space or disallow whitespace on the inside of the brackets within attribute selectors. - [`selector-attribute-operator-blacklist`](../../src/rules/selector-attribute-operator-blacklist/README.md): Specify a blacklist of disallowed attribute operators. - [`selector-attribute-operator-space-after`](../../src/rules/selector-attribute-operator-space-after/README.md): Require a single space or disallow whitespace after operators within attribute selectors. - [`selector-attribute-operator-space-before`](../../src/rules/selector-attribute-operator-space-before/README.md): Require a single space or disallow whitespace before operators within attribute selectors. - [`selector-attribute-operator-whitelist`](../../src/rules/selector-attribute-operator-whitelist/README.md): Specify a whitelist of allowed attribute operators. - [`selector-attribute-quotes`](../../src/rules/selector-attribute-quotes/README.md): Require or disallow quotes for attribute values. - [`selector-class-pattern`](../../src/rules/selector-class-pattern/README.md): Specify a pattern for class selectors. - [`selector-combinator-space-after`](../../src/rules/selector-combinator-space-after/README.md): Require a single space or disallow whitespace after the combinators of selectors. - [`selector-combinator-space-before`](../../src/rules/selector-combinator-space-before/README.md): Require a single space or disallow whitespace before the combinators of selectors. - [`selector-descendant-combinator-no-non-space`](../../src/rules/selector-descendant-combinator-no-non-space/README.md): Disallow non-space characters for descendant combinators of selectors. - [`selector-id-pattern`](../../src/rules/selector-id-pattern/README.md): Specify a pattern for id selectors. - [`selector-max-compound-selectors`](../../src/rules/selector-max-compound-selectors/README.md): Limit the number of compound selectors in a selector. - [`selector-max-specificity`](../../src/rules/selector-max-specificity/README.md): Limit the specificity of selectors. - [`selector-nested-pattern`](../../src/rules/selector-nested-pattern/README.md): Specify a pattern for the selectors of rules nested within rules. - [`selector-no-attribute`](../../src/rules/selector-no-attribute/README.md): Disallow attribute selectors. - [`selector-no-combinator`](../../src/rules/selector-no-combinator/README.md): Disallow combinators in selectors. - [`selector-no-id`](../../src/rules/selector-no-id/README.md): Disallow id selectors. - [`selector-no-qualifying-type`](../../src/rules/selector-no-qualifying-type/README.md): Disallow qualifying a selector by type. - [`selector-no-type`](../../src/rules/selector-no-type/README.md): Disallow type selectors. - [`selector-no-universal`](../../src/rules/selector-no-universal/README.md): Disallow the universal selector. - [`selector-no-vendor-prefix`](../../src/rules/selector-no-vendor-prefix/README.md): Disallow vendor prefixes for selectors. - [`selector-pseudo-class-blacklist`](../../src/rules/selector-pseudo-class-blacklist/README.md): Specify a blacklist of disallowed pseudo-class selectors. - [`selector-pseudo-class-case`](../../src/rules/selector-pseudo-class-case/README.md): Specify lowercase or uppercase for pseudo-class selectors. - [`selector-pseudo-class-no-unknown`](../../src/rules/selector-pseudo-class-no-unknown/README.md): Disallow unknown pseudo-class selectors. - [`selector-pseudo-class-parentheses-space-inside`](../../src/rules/selector-pseudo-class-parentheses-space-inside/README.md): Require a single space or disallow whitespace on the inside of the parentheses within pseudo-class selectors. - [`selector-pseudo-class-whitelist`](../../src/rules/selector-pseudo-class-whitelist/README.md): Specify a whitelist of allowed pseudo-class selectors. - [`selector-pseudo-element-case`](../../src/rules/selector-pseudo-element-case/README.md): Specify lowercase or uppercase for pseudo-element selectors. - [`selector-pseudo-element-colon-notation`](../../src/rules/selector-pseudo-element-colon-notation/README.md): Specify single or double colon notation for applicable pseudo-elements. - [`selector-pseudo-element-no-unknown`](../../src/rules/selector-pseudo-element-no-unknown/README.md): Disallow unknown pseudo-element selectors. - [`selector-root-no-composition`](../../src/rules/selector-root-no-composition/README.md): Disallow the composition of `:root` in selectors. - [`selector-type-case`](../../src/rules/selector-type-case/README.md): Specify lowercase or uppercase for type selector. - [`selector-type-no-unknown`](../../src/rules/selector-type-no-unknown/README.md): Disallow unknown type selectors. - [`selector-max-empty-lines`](../../src/rules/selector-max-empty-lines/README.md): Limit the number of adjacent empty lines within selectors. ### Selector list - [`selector-list-comma-newline-after`](../../src/rules/selector-list-comma-newline-after/README.md): Require a newline or disallow whitespace after the commas of selector lists. - [`selector-list-comma-newline-before`](../../src/rules/selector-list-comma-newline-before/README.md): Require a newline or disallow whitespace before the commas of selector lists. - [`selector-list-comma-space-after`](../../src/rules/selector-list-comma-space-after/README.md): Require a single space or disallow whitespace after the commas of selector lists. - [`selector-list-comma-space-before`](../../src/rules/selector-list-comma-space-before/README.md): Require a single space or disallow whitespace before the commas of selector lists. ### Root rule - [`root-no-standard-properties`](../../src/rules/root-no-standard-properties/README.md): Disallow standard properties inside `:root` rules. ### Rule - [`rule-nested-empty-line-before`](../../src/rules/rule-nested-empty-line-before/README.md): Require or disallow an empty line before nested rules. - [`rule-non-nested-empty-line-before`](../../src/rules/rule-non-nested-empty-line-before/README.md): Require or disallow an empty line before non-nested rules. ### Media feature - [`media-feature-colon-space-after`](../../src/rules/media-feature-colon-space-after/README.md): Require a single space or disallow whitespace after the colon in media features. - [`media-feature-colon-space-before`](../../src/rules/media-feature-colon-space-before/README.md): Require a single space or disallow whitespace before the colon in media features. - [`media-feature-name-blacklist`](../../src/rules/media-feature-name-blacklist/README.md): Specify a blacklist of disallowed media feature names. - [`media-feature-name-case`](../../src/rules/media-feature-name-case/README.md): Specify lowercase or uppercase for media feature names. - [`media-feature-name-no-unknown`](../../src/rules/media-feature-name-no-unknown/README.md): Disallow unknown media feature names. - [`media-feature-name-no-vendor-prefix`](../../src/rules/media-feature-name-no-vendor-prefix/README.md): Disallow vendor prefixes for media feature names. - [`media-feature-name-whitelist`](../../src/rules/media-feature-name-whitelist/README.md): Specify a whitelist of allowed media feature names. - [`media-feature-no-missing-punctuation`](../../src/rules/media-feature-no-missing-punctuation/README.md): Disallow missing punctuation for non-boolean media features. - [`media-feature-parentheses-space-inside`](../../src/rules/media-feature-parentheses-space-inside/README.md): Require a single space or disallow whitespace on the inside of the parentheses within media features. - [`media-feature-range-operator-space-after`](../../src/rules/media-feature-range-operator-space-after/README.md): Require a single space or disallow whitespace after the range operator in media features. - [`media-feature-range-operator-space-before`](../../src/rules/media-feature-range-operator-space-before/README.md): Require a single space or disallow whitespace before the range operator in media features. ### Custom media - [`custom-media-pattern`](../../src/rules/custom-media-pattern/README.md): Specify a pattern for custom media query names. ### Media query list - [`media-query-list-comma-newline-after`](../../src/rules/media-query-list-comma-newline-after/README.md): Require a newline or disallow whitespace after the commas of media query lists. - [`media-query-list-comma-newline-before`](../../src/rules/media-query-list-comma-newline-before/README.md): Require a newline or disallow whitespace before the commas of media query lists. - [`media-query-list-comma-space-after`](../../src/rules/media-query-list-comma-space-after/README.md): Require a single space or disallow whitespace after the commas of media query lists. - [`media-query-list-comma-space-before`](../../src/rules/media-query-list-comma-space-before/README.md): Require a single space or disallow whitespace before the commas of media query lists. ### At-rule - [`at-rule-blacklist`](../../src/rules/at-rule-blacklist/README.md): Specify a blacklist of disallowed at-rules. - [`at-rule-empty-line-before`](../../src/rules/at-rule-empty-line-before/README.md): Require or disallow an empty line before at-rules. - [`at-rule-name-case`](../../src/rules/at-rule-name-case/README.md): Specify lowercase or uppercase for at-rules names. - [`at-rule-name-newline-after`](../../src/rules/at-rule-name-newline-after/README.md): Require a newline after at-rule names. - [`at-rule-name-space-after`](../../src/rules/at-rule-name-space-after/README.md): Require a single space after at-rule names. - [`at-rule-no-unknown`](../../src/rules/at-rule-no-unknown/README.md): Disallow unknown at-rules. - [`at-rule-no-vendor-prefix`](../../src/rules/at-rule-no-vendor-prefix/README.md): Disallow vendor prefixes for at-rules. - [`at-rule-semicolon-newline-after`](../../src/rules/at-rule-semicolon-newline-after/README.md): Require a newline after the semicolon of at-rules. - [`at-rule-whitelist`](../../src/rules/at-rule-whitelist/README.md): Specify a whitelist of allowed at-rules. ### `stylelint-disable` comment - [`stylelint-disable-reason`](../../src/rules/stylelint-disable-reason/README.md): Require a reason comment before or after `stylelint-disable` comments. ### Comment - [`comment-empty-line-before`](../../src/rules/comment-empty-line-before/README.md): Require or disallow an empty line before comments. - [`comment-no-empty`](../../src/rules/comment-no-empty/README.md): Disallow empty comments. - [`comment-whitespace-inside`](../../src/rules/comment-whitespace-inside/README.md): Require or disallow whitespace on the inside of comment markers. - [`comment-word-blacklist`](../../src/rules/comment-word-blacklist/README.md): Specify a blacklist of disallowed words within comments. ### General / Sheet - [`indentation`](../../src/rules/indentation/README.md): Specify indentation. - [`max-empty-lines`](../../src/rules/max-empty-lines/README.md): Limit the number of adjacent empty lines. - [`max-line-length`](../../src/rules/max-line-length/README.md): Limit the length of a line. - [`max-nesting-depth`](../../src/rules/max-nesting-depth/README.md): Limit the depth of nesting. - [`no-browser-hacks`](../../src/rules/no-browser-hacks/README.md): Disallow browser hacks that are irrelevant to the browsers you are targeting. - [`no-descending-specificity`](../../src/rules/no-descending-specificity/README.md): Disallow selectors of lower specificity from coming after overriding selectors of higher specificity. - [`no-duplicate-selectors`](../../src/rules/no-duplicate-selectors/README.md): Disallow duplicate selectors. - [`no-empty-source`](../../src/rules/no-empty-source/README.md): Disallow empty sources. - [`no-eol-whitespace`](../../src/rules/no-eol-whitespace/README.md): Disallow end-of-line whitespace. - [`no-extra-semicolons`](../../src/rules/no-extra-semicolons/README.md): Disallow extra semicolons. - [`no-indistinguishable-colors`](../../src/rules/no-indistinguishable-colors/README.md): Disallow colors that are suspiciously close to being identical. - [`no-invalid-double-slash-comments`](../../src/rules/no-invalid-double-slash-comments/README.md): Disallow double-slash comments (`//...`) which are not supported by CSS. - [`no-missing-end-of-source-newline`](../../src/rules/no-missing-end-of-source-newline/README.md): Disallow missing end-of-source newlines. - [`no-unknown-animations`](../../src/rules/no-unknown-animations/README.md): Disallow animation names that do not correspond to a `@keyframes` declaration. - [`no-unsupported-browser-features`](../../src/rules/no-unsupported-browser-features/README.md): Disallow features that are unsupported by the browsers that you are targeting.