--- title: Dart Sass Command-Line Interface table_of_contents: true complementary_content: | --- {% markdown %} ## Usage The Dart Sass executable can be invoked in one of two modes. ### One-to-One Mode ``` sass [output.css] ``` One-to-one mode compiles a single input file (`input.scss`) to a single output location (`output.css`). If no output location is passed, the compiled CSS is printed to the terminal. The input file is parsed as [SCSS][] if its extension is `.scss`, as the [indented syntax][] if its extension is `.sass`, or as [plain CSS][] if its extension is `.css`. If it doesn't have one of these three extensions, or if it comes from standard input, it's parsed as SCSS by default. This can be controlled with the [`--indented` flag][]. [SCSS]: /documentation/syntax#scss [indented syntax]: /documentation/syntax#the-indented-syntax [plain CSS]: /documentation/at-rules/import#importing-css [`--indented` flag]: #indented The special string `-` can be passed in place of the input file to tell Sass to read the input file from [standard input][]. Sass will default to parsing it as SCSS unless the [`--indented` flag][] is passed. [standard input]: https://en.wikipedia.org/wiki/Standard_streams#Standard_input_(stdin) ### Many-to-many Mode {% compatibility '1.4.0' %}{% endcompatibility %} ``` sass [:] [:]... ``` Many-to-many mode compiles one or more input files to one or more output files. The inputs are separated from the outputs with colons. It can also compile all Sass files in a directory to CSS files with the same names in another directory. ```shellsession ​# Compiles style.scss to style.css. $ sass style.scss:style.css ​# Compiles light.scss and dark.scss to light.css and dark.css. $ sass light.scss:light.css dark.scss:dark.css ​# Compiles all Sass files in themes/ to CSS files in public/css/. $ sass themes:public/css ``` When compiling whole directories, Sass will ignore [partial files][] whose names begin with `_`. You can use partials to separate out your stylesheets without creating a bunch of unnecessary output files. [partial files]: /documentation/at-rules/import#partials ## Options ### Input and Output These options control how Sass loads its input files and how it produces output files. #### `--stdin` This flag is an alternative way of telling Sass that it should read its input file from [standard input][]. When it's passed, no input file may be passed. ```shellsession $ echo "h1 {font-size: 40px}" | sass --stdin h1.css $ echo "h1 {font-size: 40px}" | sass --stdin h1 { font-size: 40px; } ``` The `--stdin` flag may not be used with [many-to-many mode][]. [many-to-many mode]: #many-to-many-mode #### `--indented` This flag tells Sass to parse the input file as the [indented syntax][]. If it's used in [many-to-many mode][], all input files are parsed as the indented syntax, although files they [use][] will have their syntax determined as usual. The inverse, `--no-indented`, can be used to force all input files to be parsed as [SCSS][] instead. [use]: /documentation/at-rules/use The `--indented` flag is mostly useful when the input file is coming from [standard input][], so its syntax can't be automatically determined. ```shellsession $ echo -e 'h1\n font-size: 40px' | sass --indented - h1 { font-size: 40px; } ``` #### `--load-path` This option (abbreviated `-I`) adds an additional [load path][] for Sass to look for stylesheets. It can be passed multiple times to provide multiple load paths. Earlier load paths will take precedence over later ones. [load path]: /documentation/at-rules/use#load-paths ```shellsession $ sass --load-path=node_modules/bootstrap/dist/css style.scss style.css ``` #### `--style` This option (abbreviated `-s`) controls the output style of the resulting CSS. Dart Sass supports two output styles: - `expanded` (the default) writes each selector and declaration on its own line. - `compressed` removes as many extra characters as possible, and writes the entire stylesheet on a single line. ```shellsession $ sass --style=expanded style.scss h1 { font-size: 40px; } $ sass --style=compressed style.scss h1{font-size:40px} ``` #### `--no-charset` {% compatibility '1.19.0' %}{% endcompatibility %} This flag tells Sass never to emit a `@charset` declaration or a UTF-8 [byte-order mark][]. By default, or if `--charset` is passed, Sass will insert either a `@charset` declaration (in expanded output mode) or a byte-order mark (in compressed output mode) if the stylesheet contains any non-ASCII characters. [byte-order mark]: https://en.wikipedia.org/wiki/Byte_order_mark#UTF-8 ```shellsession $ echo 'h1::before {content: "👭"}' | sass --no-charset h1::before { content: "👭"; } $ echo 'h1::before {content: "👭"}' | sass --charset @charset "UTF-8"; h1::before { content: "👭"; } ``` #### `--error-css` {% compatibility '1.20.0' %}{% endcompatibility %} This flag tells Sass whether to emit a CSS file when an error occurs during compilation. This CSS file describes the error in a comment _and_ in the `content` property of `body::before`, so that you can see the error message in the browser without needing to switch back to the terminal. By default, error CSS is enabled if you're compiling to at least one file on disk (as opposed to standard output). You can pass `--error-css` explicitly to enable it even when you're compiling to standard out, or `--no-error-css` to disable it everywhere. When it's disabled, the [`--update` flag][] and [`--watch` flag][] will delete CSS files instead when an error occurs. [`--watch` flag]: #watch ```shellsession $ sass --error-css style.scss style.css /* Error: Incompatible units em and px. * , * 1 | $width: 15px + 2em; * | ^^^^^^^^^^ * ' * test.scss 1:9 root stylesheet */ body::before { font-family: "Source Code Pro", "SF Mono", Monaco, Inconsolata, "Fira Mono", "Droid Sans Mono", monospace, monospace; white-space: pre; display: block; padding: 1em; margin-bottom: 1em; border-bottom: 2px solid black; content: "Error: Incompatible units em and px.\a \2577 \a 1 \2502 $width: 15px + 2em;\a \2502 ^^^^^^^^^^\a \2575 \a test.scss 1:9 root stylesheet"; } Error: Incompatible units em and px. ╷ 1 │ $width: 15px + 2em; │ ^^^^^^^^^^ ╵ test.scss 1:9 root stylesheet ``` #### `--update` {% compatibility '1.4.0' %}{% endcompatibility %} If the `--update` flag is passed, Sass will only compile stylesheets whose dependencies have been modified more recently than the corresponding CSS file was generated. It will also print status messages when updating stylesheets. ```shellsession $ sass --update themes:public/css Compiled themes/light.scss to public/css/light.css. ``` ### Source Maps {% compatibility '1.3.0' %}{% endcompatibility %} {% include 'documentation/snippets/source-maps.liquid' %} Dart Sass generates source maps by default for every CSS file it emits. #### `--no-source-map` If the `--no-source-map` flag is passed, Sass won't generate any source maps. it cannot be passed along with other source map options. ```shellsession $ sass --no-source-map style.scss style.css ``` #### `--source-map-urls` This option controls how the source maps that Sass generates link back to the Sass files that contributed to the generated CSS. Dart Sass supports two types of URLs: - `relative` (the default) uses relative URLs from the location of the source map file to the locations of the Sass source file. - `absolute` uses the absolute [`file:` URLs][] of the Sass source files. Note that absolute URLs will only work on the same computer that the CSS was compiled. [`file:` URLs]: https://en.wikipedia.org/wiki/File_URI_scheme ```shellsession ​# Generates a URL like /documentation/sass/style.scss". $ sass --source-map-urls=relative sass/style.scss css/style.css ​# Generates a URL like "file:///home/style-wiz/sassy-app/sass/style.scss". $ sass --source-map-urls=absolute sass/style.scss css/style.css ``` #### `--embed-sources` This flag tells Sass to embed the entire contents of the Sass files that contributed to the generated CSS in the source map. This may produce very large source maps, but it guarantees that the source will be available on any computer no matter how the CSS is served. ```shellsession $ sass --embed-sources sass/style.scss css.style.css ``` #### `--embed-source-map` This flag tells Sass to embed the contents of the source map file in the generated CSS, rather than creating a separate file and linking to it from the CSS. ```shellsession $ sass --embed-source-map sass/style.scss css.style.css ``` ### Other Options #### `--watch` {% compatibility '1.6.0' %}{% endcompatibility %} This flag (abbreviated `-w`) acts like the [`--update` flag][], but after the first round compilation is done Sass stays open and continues compiling stylesheets whenever they or their dependencies change. [`--update` flag]: #update Sass watches only the directories that you pass as-is on the command line, parent directories of filenames you pass on the command line, and load paths. It does not watch additional directories based on a file's `@import`/`@use`/ `@forward` rules. ```shellsession $ sass --watch themes:public/css Compiled themes/light.scss to public/css/light.css. ​# Then when you edit themes/dark.scss... Compiled themes/dark.scss to public/css/dark.css. ``` #### `--poll` {% compatibility '1.8.0' %}{% endcompatibility %} This flag, which may only be passed along with `--watch`, tells Sass to manually check for changes to the source files every so often instead of relying on the operating system to notify it when something changes. This may be necessary if you're editing Sass on a remote drive where the operating system's notification system doesn't work. ```shellsession $ sass --watch --poll themes:public/css Compiled themes/light.scss to public/css/light.css. ​# Then when you edit themes/dark.scss... Compiled themes/dark.scss to public/css/dark.css. ``` #### `--stop-on-error` {% compatibility '1.8.0' %}{% endcompatibility %} This flag tells Sass to stop compiling immediately when an error is detected, rather than trying to compile other Sass files that may not contain errors. It's mostly useful in [many-to-many mode][]. ```shellsession $ sass --stop-on-error themes:public/css Error: Expected expression. ╷ 42 │ h1 {font-face: } │ ^ ╵ themes/light.scss 42:16 root stylesheet ``` #### `--interactive` {% compatibility '1.5.0' %}{% endcompatibility %} This flag (abbreviated `-i`) tells Sass to run in interactive mode, where you can write [SassScript expressions][] and see their results. Interactive mode also supports [variables][] and [`@use` rules][]. [SassScript expressions]: /documentation/syntax/structure#expressions [variables]: /documentation/variables [`@use` rules]: /documentation/at-rules/use ```shellsession $ sass --interactive >> 1px + 1in 97px >> @use "sass:map" >> $map: ("width": 100px, "height": 70px) ("width": 100px, "height": 70px) >> map.get($map, "width") 100px ``` #### `--color` This flag (abbreviated `-c`) tells Sass to emit [terminal colors][], and the inverse `--no-color` tells it not to emit colors. By default, it will emit colors if it looks like it's being run on a terminal that supports them. [terminal colors]: https://en.wikipedia.org/wiki/ANSI_escape_code#Colors 
$ sass --color style.scss style.css
Error: Incompatible units em and px.
  ╷
1 │ $width: 15px + 2em
  │         ^^^^^^^^^^
  ╵
  style.scss 1:9  root stylesheet

$ sass --no-color style.scss style.css
Error: Incompatible units em and px.
  ╷
1 │ $width: 15px + 2em
  │         ^^^^^^^^^^
  ╵
  style.scss 1:9  root stylesheet
#### `--no-unicode` {% compatibility '1.17.0' %}{% endcompatibility %} This flag tells Sass only to emit ASCII characters to the terminal as part of error messages. By default, or if `--unicode` is passed, Sass will emit non-ASCII characters for these messages. This flag does not affect the CSS output. ```shellsession $ sass --no-unicode style.scss style.css Error: Incompatible units em and px. , 1 | $width: 15px + 2em; | ^^^^^^^^^^ ' test.scss 1:9 root stylesheet $ sass --unicode style.scss style.css Error: Incompatible units em and px. ╷ 1 │ $width: 15px + 2em; │ ^^^^^^^^^^ ╵ test.scss 1:9 root stylesheet ``` #### `--quiet` This flag (abbreviated `-q`) tells Sass not to emit any warnings when compiling. By default, Sass emits warnings when deprecated features are used or when the [`@warn` rule][] is encountered. It also silences the [`@debug` rule][]. [`@warn` rule]: /documentation/at-rules/warn [`@debug` rule]: /documentation/at-rules/debug ```shellsession $ sass --quiet style.scss style.css ``` #### `--quiet-deps` This flag tells Sass not to emit deprecation warnings that come from dependencies. It considers any file that's transitively imported through a [load path] to be a "dependency". This flag doesn't affect the [`@warn` rule] or the [`@debug` rule]. ```shellsession $ sass --load-path=node_modules --quiet-deps style.scss style.css ``` #### `--fatal-deprecation` {% compatibility '1.59.0' %}{% endcompatibility %} This option tells Sass to treat a particular type of deprecation warning as an error. For example, this command tells Sass to treat deprecation warnings for `/`-as-division as errors: ```shellsession $ sass --fatal-deprecation=slash-div style.scss style.css Error: Using / for division outside of calc() is deprecated and will be removed in Dart Sass 2.0.0. Recommendation: math.div(4, 2) or calc(4 / 2) More info and automated migrator: https://sass-lang.com/d/slash-div This is only an error because you've set the slash-div deprecation to be fatal. Remove this setting if you need to keep using this feature. ╷ 1 │ a { b: (4/2); } │ ^^^ ╵ style.scss 1:9 root stylesheet ``` The following deprecation IDs can be passed to this option:
ID Version Description
call-string 0.0.0 Passing a string directly to meta.call().
elseif 1.3.2 Using @elseif instead of @else if.
moz-document 1.7.2 Using @-moz-document (except for the empty url prefix hack).
new-global 1.17.2 Declaring new variables with !global.
color-module-compat 1.23.0 Using color module functions in place of plain CSS functions.
slash-div 1.33.0 Using the / operator for division.
bogus-combinators 1.54.0 Leading, trailing, and repeated combinators.
strict-unary 1.55.0 Ambiguous + and - operators.
function-units 1.56.0 Passing invalid units to built-in functions.
duplicate-var-flags 1.62.0 Using multiple copies of !global or !default in a single variable declaration.
Alternatively, you can pass a Dart Sass version to treat all deprecations that were present in that version as errors. For example, `--fatal-deprecation=1.33.0` would treat all deprecations in the table above up to and including `slash-div` as errors, but leave any newer deprecations as warnings. #### `--trace` This flag tells Sass to print the full Dart or JavaScript stack trace when an error is encountered. It's used by the Sass team for debugging errors. ```shellsession $ sass --trace style.scss style.css Error: Expected expression. ╷ 42 │ h1 {font-face: } │ ^ ╵ themes/light.scss 42:16 root stylesheet package:sass/src/visitor/evaluate.dart 1846:7 _EvaluateVisitor._addExceptionSpan package:sass/src/visitor/evaluate.dart 1128:12 _EvaluateVisitor.visitBinaryOperationExpression package:sass/src/ast/sass/expression/binary_operation.dart 39:15 BinaryOperationExpression.accept package:sass/src/visitor/evaluate.dart 1097:25 _EvaluateVisitor.visitVariableDeclaration package:sass/src/ast/sass/statement/variable_declaration.dart 50:15 VariableDeclaration.accept package:sass/src/visitor/evaluate.dart 335:13 _EvaluateVisitor.visitStylesheet package:sass/src/visitor/evaluate.dart 323:5 _EvaluateVisitor.run package:sass/src/visitor/evaluate.dart 81:10 evaluate package:sass/src/executable/compile_stylesheet.dart 59:9 compileStylesheet package:sass/src/executable.dart 62:15 main ``` #### `--help` This flag (abbreviated `-h`) prints a summary of this documentation. ```shellsession $ sass --help Compile Sass to CSS. Usage: sass [output.css] sass : : ... ``` #### `--version` This flag prints the current version of Sass. ```shellsession $ sass --version {{ releases['dart-sass'].version }} ``` {% endmarkdown %}