Breaking Change: -moz-document

Firefox used to have a @-moz-document rule requiring special parsing. As support is removed from Firefox, Sass is in the process of removing support for parsing them.

Sass has historically supported a special parsing for the @-moz-document rule. As Firefox dropped support for them, Sass will also drop support for the special parsing and will treat it as an unknown at-rule.

There is one exception: an empty url prefix function is still allowed, as that’s used in a hack targetting Firefox.

SCSS Syntax

@-moz-document url-prefix() {
  .error {
    color: red;
  }
}

Sass Syntax

@-moz-document url-prefix()
  .error
    color: red

CSS Output

@-moz-document url-prefix() {
  .error {
    color: red;
  }
}

Transition PeriodTransition Period permalink

Compatibility:
Dart Sass
since 1.7.2
LibSass
✗
Ruby Sass
✗

First, we’ll emit deprecation warnings for all usages of @-moz-document except for the empty url-prefix hack.

In Dart Sass 2.0, @-moz-document will be treated as an unknown at-rule.

Can I Silence the Warnings?Can I Silence the Warnings? permalink

Sass provides a powerful suite of options for managing which deprecation warnings you see and when.

Terse and Verbose ModeTerse and Verbose Mode permalink

By default, Sass runs in terse mode, where it will only print each type of deprecation warning five times before it silences additional warnings. This helps ensure that users know when they need to be aware of an upcoming breaking change without creating an overwhelming amount of console noise.

If you run Sass in verbose mode instead, it will print every deprecation warning it encounters. This can be useful for tracking the remaining work to be done when fixing deprecations. You can enable verbose mode using the --verbose flag on the command line, or the verbose option in the JavaScript API.

⚠️ Heads up!

When running from the JS API, Sass doesn’t share any information across compilations, so by default it’ll print five warnings for each stylesheet that’s compiled. However, you can fix this by writing (or asking the author of your favorite framework’s Sass plugin to write) a custom Logger that only prints five errors per deprecation and can be shared across multiple compilations.

Silencing Deprecations in DependenciesSilencing Deprecations in Dependencies permalink

Sometimes, your dependencies have deprecation warnings that you can’t do anything about. You can silence deprecation warnings from dependencies while still printing them for your app using the --quiet-deps flag on the command line, or the quietDeps option in the JavaScript API.

For the purposes of this flag, a "dependency" is any stylesheet that’s not just a series of relative loads from the entrypoint stylesheet. This means anything that comes from a load path, and most stylesheets loaded through custom importers.

Silencing Specific DeprecationsSilencing Specific Deprecations permalink

If you know that one particular deprecation isn’t a problem for you, you can silence warnings for that specific deprecation using the --silence-deprecation flag on the command line, or the silenceDeprecations option in the JavaScript API.

⚠️ Heads up!

This option is only available in the modern JS API.