Dart Sass Command-Line Interface

UsageUsage permalink

The Dart Sass executable can be invoked in one of two modes.

One-to-One ModeOne-to-One Mode permalink

sass <input.scss> [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.

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.

Many-to-Many ModeMany-to-Many Mode permalink

Dart Sass: since 1.4.0

sass [<input.scss>:<output.css>] [<input/>:<output/>]...

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.

# 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.

OptionsOptions permalink

Input and OutputInput and Output permalink

These options control how Sass loads its input files and how it produces output files.

`--stdin`–stdin permalink

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.

$ 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.

`--indented`–indented permalink

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.

The --indented flag is mostly useful when the input file is coming from standard input, so its syntax can’t be automatically determined.

$ echo -e 'h1\n  font-size: 40px' | sass --indented -
h1 {
  font-size: 40px;
}

`--load-path`–load-path permalink

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.

$ sass --load-path=node_modules/bootstrap/dist/css style.scss style.css

`--pkg-importer=node`–pkg-importer=node permalink

Dart Sass: since 1.71.0

This option (abbreviated -p node) adds the Node.js pkg: importer to the end of the load path, so that stylesheets can load dependencies using the Node.js module resolution algorithm.

Support for additional built-in pkg: importers may be added in the future.

$ sass --pkg-importer=node style.scss style.css

`--style`–style permalink

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.

$ sass --style=expanded style.scss
h1 {
  font-size: 40px;
}

$ sass --style=compressed style.scss
h1{font-size:40px}

`--no-charset`–no-charset permalink

Dart Sass: since 1.19.0

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.

$ echo 'h1::before {content: "👭"}' | sass --no-charset
h1::before {
  content: "👭";
}

$ echo 'h1::before {content: "👭"}' | sass --charset
@charset "UTF-8";
h1::before {
  content: "👭";
}

`--error-css`–error-css permalink

Dart Sass: since 1.20.0

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.

$ 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`–update permalink

Dart Sass: since 1.4.0

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.

$ sass --update themes:public/css
Compiled themes/light.scss to public/css/light.css.

Source MapsSource Maps permalink

Dart Sass: since 1.3.0

Source maps are files that tell browsers or other tools that consume CSS how that CSS corresponds to the Sass files from which it was generated. They make it possible to see and even edit your Sass files in browsers. See instructions for using source maps in Chrome and Firefox.

Dart Sass generates source maps by default for every CSS file it emits.

`--no-source-map`–no-source-map permalink

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.

$ sass --no-source-map style.scss style.css

`--source-map-urls`–source-map-urls permalink

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.

# Generates a URL like "../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`–embed-sources permalink

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.

$ sass --embed-sources sass/style.scss css.style.css

`--embed-source-map`–embed-source-map permalink

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.

$ sass --embed-source-map sass/style.scss css.style.css

Other OptionsOther Options permalink

`--watch`–watch permalink

Dart Sass: since 1.6.0

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.

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.

$ 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`–poll permalink

Dart Sass: since 1.8.0

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.

$ 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`–stop-on-error permalink

Dart Sass: since 1.8.0

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.

$ sass --stop-on-error themes:public/css
Error: Expected expression.
   ╷
42 │ h1 {font-face: }
   │                ^
   ╵
  themes/light.scss 42:16  root stylesheet

`--interactive`–interactive permalink

Dart Sass: since 1.5.0

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.

$ sass --interactive
>> 1px + 1in
97px
>> @use "sass:map"
>> $map: ("width": 100px, "height": 70px)
("width": 100px, "height": 70px)
>> map.get($map, "width")
100px

`--color`–color permalink

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.

$ 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`–no-unicode permalink

Dart Sass: since 1.17.0

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.

$ 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`–quiet permalink

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.

$ sass --quiet style.scss style.css

`--quiet-deps`–quiet-deps permalink

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.

$ sass --load-path=node_modules --quiet-deps style.scss style.css

`--fatal-deprecation`–fatal-deprecation permalink

Dart Sass: since 1.59.0

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:

$ 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: /documentation/breaking-changes/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	Deprecated In	Description
`call-string`	0.0.0	Passing a string directly to meta.call().
`elseif`	1.3.2	@elseif.
`moz-document`	1.7.2	@-moz-document.
`relative-canonical`	1.14.2	Imports using relative canonical URLs.
`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	/ 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 !default or !global multiple times for one variable.
`null-alpha`	1.62.3	Passing null as alpha in the JS API.
`abs-percent`	1.65.0	Passing percentages to the Sass abs() function.
`fs-importer-cwd`	1.73.0	Using the current working directory as an implicit load path.
`css-function-mixin`	1.76.0	Function and mixin names beginning with –.

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.

`--future-deprecation`–future-deprecation permalink

Dart Sass: since 1.59.0

This option tells Sass to opt-in to a future type of deprecation warning early, emitting warnings even though the deprecation is not yet active. This option can be combined with --fatal-deprecation to emit errors instead of warnings for a future deprecation.

$ sass --future-deprecation=import style.scss style.css
Deprecation Warning on line 1, column 9 of style.scss:
Sass @import rules will be deprecated in the future.
Remove the --future-deprecation=import flag to silence this warning for now.
  ╷
1 │ @import 'dependency';
  │         ^^^^^^^^^^^^
  ╵

The following deprecation IDs can be passed to this option:

ID	Description
`import`	@import rules.

`--silence-deprecation`–silence-deprecation permalink

Dart Sass: since 1.74.0

This option tells Sass to silence a particular type of deprecation warning if you wish to temporarily ignore the deprecation. Any of the deprecations listed in the --fatal-deprecation section above can be passed here, though passing in a version is not supported.

$ sass --silence-deprecation=slash-div style.scss style.css

`--trace`–trace permalink

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.

$ 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`–help permalink

This flag (abbreviated -h) prints a summary of this documentation.

$ sass --help
Compile Sass to CSS.

Usage: sass <input.scss> [output.css]
       sass <input.scss>:<output.css> <input/>:<output/>

...

`--version`–version permalink

This flag prints the current version of Sass.

$ sass --version
1.77.6

Dart Sass Command-Line Interface

UsageUsage permalink

One-to-One ModeOne-to-One Mode permalink

Many-to-Many ModeMany-to-Many Mode permalink

OptionsOptions permalink

Input and OutputInput and Output permalink

--stdin–stdin permalink

--indented–indented permalink

--load-path–load-path permalink

--pkg-importer=node–pkg-importer=node permalink

--style–style permalink

--no-charset–no-charset permalink

--error-css–error-css permalink

--update–update permalink

Source MapsSource Maps permalink

--no-source-map–no-source-map permalink

--source-map-urls–source-map-urls permalink

--embed-sources–embed-sources permalink

--embed-source-map–embed-source-map permalink

Other OptionsOther Options permalink

--watch–watch permalink

--poll–poll permalink

--stop-on-error–stop-on-error permalink

--interactive–interactive permalink

--color–color permalink

--no-unicode–no-unicode permalink

--quiet–quiet permalink

--quiet-deps–quiet-deps permalink

--fatal-deprecation–fatal-deprecation permalink

--future-deprecation–future-deprecation permalink

--silence-deprecation–silence-deprecation permalink

--trace–trace permalink

--help–help permalink

--version–version permalink