fast-sass-loader

2.0.1 verified Sat Apr 25 auth: no javascript maintenance

A webpack loader for Sass/SCSS that claims 5-10x faster compilation than sass-loader by deduplicating @imports, merging all Sass files into a single compile unit, and caching results internally. Version 2.x switched from node-sass to dart-sass (npm 'sass') as the default compiler, with an `implementation` option to restore node-sass. It also provides built-in url() resolution, eliminating the need for resolve-url-loader. Key trade-offs include no source map support and limited loader configuration compared to sass-loader. Release cadence is low; last update was 2020. Requires webpack 1–5 and sass 1.x as peer dependencies.

Common errors

error Module not found: Error: Cannot resolve module 'sass' ↓

cause Missing peer dependency 'sass' (or 'node-sass' if configured).

fix

npm install sass --save-dev

error Error: fast-sass-loader: no implementation found, you should install 'sass' or 'node-sass' peer dependency ↓

cause Neither dart-sass nor node-sass is installed.

fix

Install either: npm install sass --save-dev OR npm install node-sass --save-dev

error TypeError: this.getOptions is not a function ↓

cause Using fast-sass-loader with webpack version below 4 (requires getOptions API).

fix

Upgrade webpack to version 4 or later, or pin fast-sass-loader to version 1.x.

Warnings

breaking In v2.x, default implementation changed from node-sass to dart-sass (npm sass). Existing projects relying on node-sass may fail. ↓

fix Set options.implementation to require('node-sass') in webpack config, or migrate to dart-sass syntax.

gotcha No source map support. If you need source maps for debugging, use sass-loader instead. ↓

fix Switch to sass-loader or disable source map requirement for Sass.

gotcha Loader configuration options like 'includePaths' are passed directly to the Sass compiler, not all sass-loader options are supported. ↓

fix Refer to the fast-sass-loader documentation for supported options; common missing options include 'sourceMap' and 'outputStyle'.

deprecated The package has not been updated since 2020 and may not be compatible with webpack 5+ or latest dart-sass. ↓

fix Consider sass-loader for active support, or fork the project to apply updates.

Install

npm install fast-sass-loader

yarn add fast-sass-loader

pnpm add fast-sass-loader

Imports

fast-sass-loader
wrong
```
const FastSassLoader = require('fast-sass-loader').default
```
correct
```
import FastSassLoader from 'fast-sass-loader'
```
CommonJS require works without .default: const loader = require('fast-sass-loader')

Quickstart

Shows a basic webpack config using fast-sass-loader with includePaths and data options, paired with css-loader.

// webpack.config.js
module.exports = {
  module: {
    rules: [
      {
        test: /\.(scss|sass)$/,
        use: [
          'css-loader',
          {
            loader: 'fast-sass-loader',
            options: {
              includePaths: ['src/styles'],
              data: '$env: production;'
            }
          }
        ]
      }
    ]
  }
};